Substract shortest string containing all search criteria

Substract shortest string containing all search criteria - c#

I have a problem to solve where given a string source and a collection of search criteria criteria, the algorithm has to return the shortest possible substring of source that contains all items of criteria.
=================================
UPDATE
The same search criteria might be in the source string multiple
times. In that case, it is required to return the sub-string
containing the particular instance of the search criteria such that
it is the shortest among all possible sub-strings.
The search items can contain spaces in them such as hello world
The order in which the search criteria are found does not matter as long as they are all in the resultant sub-string
==================================
String source = "aaa wwwww fgffsd ththththt sss sgsgsgsghs bfbfb hhh sdfg kkk dhdhtrherhrhrthrthrt ddfhdetehehe kkk wdwd aaa vcvc hhh zxzx sss nbnbn";
List<String> criteria = new List<string> { "kkk", "aaa", "sss", "hhh" };
The input above should return the following substring: kkk wdwd aaa vcvc hhh zxzx sss
Unfortunately, I spent a lot of time trying to write such an algorithm but I couldn't get it just right. Below is the code I have got so far:
public struct Extraction
{
public int Start { get; set; }
public int End { get; set; }
public int Length
{
get
{
var length = this.End - this.Start;
return length;
}
}
public Extraction(int start, int end)
{
this.Start = start;
this.End = end;
}
}
public class TextExtractor
{
private String _source;
private Dictionary<String, List<Int32>> _criteriaIndexes;
private Dictionary<String, int> _entryIndex;
public TextExtractor(String source, List<String> searchCriteria)
{
this._source = source;
this._criteriaIndexes = this.ExtractIndexes(source, searchCriteria);
this._entryIndex = _criteriaIndexes.ToDictionary(x => x.Key, v => 0);
}
public String Extract()
{
List<Extraction> possibleExtractions = new List<Extraction>();
int index = 0;
int min = int.MaxValue;
int max = 0;
bool shouldStop = false;
while (index < _criteriaIndexes.Count && !shouldStop)
{
Boolean compareWithAll = index == _criteriaIndexes.Count - 1;
if (!compareWithAll)
{
var current = _criteriaIndexes.ElementAt(index);
this.CalculateMinMax(current, ref min, ref max);
index++;
}
else
{
var entry = _criteriaIndexes.Last();
while (_entryIndex[entry.Key] < entry.Value.Count)
{
int a = min;
int b = max;
this.CalculateMinMax(entry, ref a, ref b);
_entryIndex[entry.Key]++;
Extraction ext = new Extraction(a, b);
possibleExtractions.Add(ext);
}
int k = index - 1;
while (k >= 0)
{
var prev = _criteriaIndexes.ElementAt(k);
if (prev.Value.Count - 1 > _entryIndex[prev.Key])
{
_entryIndex[prev.Key]++;
break;
}
else
{
k--;
}
}
shouldStop = _criteriaIndexes.All(x => x.Value.Count - 1 <= _entryIndex[x.Key]);
_entryIndex[entry.Key] = 0;
index = 0;
min = int.MaxValue;
max = 0;
}
}
Extraction shortest = possibleExtractions.First(x => x.Length.Equals(possibleExtractions.Min(p => p.Length)));
String result = _source.Substring(shortest.Start, shortest.Length);
return result;
}
private Dictionary<String, List<Int32>> ExtractIndexes(String source, List<String> searchCriteria)
{
Dictionary<String, List<Int32>> result = new Dictionary<string, List<int>>();
foreach (var criteria in searchCriteria)
{
Int32 i = 0;
Int32 startingIndex = 0;
var indexes = new List<int>();
while (i > -1)
{
i = source.IndexOf(criteria, startingIndex);
if (i > -1)
{
startingIndex = i + 1;
indexes.Add(i);
}
}
if (indexes.Any())
{
result.Add(criteria, indexes);
}
}
return result;
}
private void CalculateMinMax(KeyValuePair<String, List<int>> current, ref int min, ref int max)
{
int j = current.Value[_entryIndex[current.Key]];
if (j < min)
{
min = j;
}
int indexPlusWordLength = j + current.Key.Length;
if (indexPlusWordLength > max)
{
max = indexPlusWordLength;
}
}
}
I would appreciate it if someone could point out where did I go wrong in my algorithm. Moreover, I kinda feel this is a very naive implementation. Maybe there is a better approach to solve this problem than trying to try out combinations of indexes?
Thanks!

This is a much simpler algorithm that will give you the shortest substring.
void Main()
{
String source = "aaa wwwww fgffsd ththththt sss ww sgsgsgsghs bfbfb hhh sdfg kkk " +
"dhdhtrherhrhrthrthrt ddfhdetehehe kkk wdwd aaa vcvc hhh zxzx sss ww nbnbn";
List<String> criteria = new List<string> { "kkk", "aaa", "sss ww", "hhh" };
var result = GetAllSubstringContainingCriteria(source, criteria)
.OrderBy(sub => sub.Length).FirstOrDefault();
// result is "kkk wdwd aaa vcvc hhh zxzx sss ww"
}
private IEnumerable<string> GetAllSubstringContainingCriteria(
string source, List<string> criteria)
{
for (int i = 0; i < source.Length; i++)
{
var subString = source.Substring(i);
if (criteria.Any(crit => subString.StartsWith(crit)))
{
var lastWordIndex =
GetLastCharacterIndexFromLastCriteriaInSubstring(subString, criteria);
if (lastWordIndex >= 0)
yield return string.Join(" ", subString.Substring(0, lastWordIndex));
}
else
continue;
}
}
private int GetLastCharacterIndexFromLastCriteriaInSubstring(
string subString, List<string> criteria)
{
var results = criteria.Select(crit => new {
index = subString.IndexOf(crit),
criteria = crit});
return results.All(result => result.index >= 0)
? results.Select(result => result.index + result.criteria.Length).Max()
: -1;
}

Let the Java built-in classes do the work. How about converting your criteria to a regular expression Pattern. If the criteria are X or Y or Z . . ., convert this into a regular expression of the form "(X)|(Y)|(Z)|...", compile it, and execute it against the source string.
This, of course, returns the leftmost match. You could code a very straightforward loop that iterates across all occurrences, caches them, and chooses the shortest--or the leftmost shortest--or, if two or more are equally short, then all of those.

Related

Sort order of files [duplicate]

Anyone have a good resource or provide a sample of a natural order sort in C# for an FileInfo array? I am implementing the IComparer interface in my sorts.

The easiest thing to do is just P/Invoke the built-in function in Windows, and use it as the comparison function in your IComparer:
[DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
private static extern int StrCmpLogicalW(string psz1, string psz2);
Michael Kaplan has some examples of how this function works here, and the changes that were made for Vista to make it work more intuitively. The plus side of this function is that it will have the same behaviour as the version of Windows it runs on, however this does mean that it differs between versions of Windows so you need to consider whether this is a problem for you.
So a complete implementation would be something like:
[SuppressUnmanagedCodeSecurity]
internal static class SafeNativeMethods
{
[DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
public static extern int StrCmpLogicalW(string psz1, string psz2);
}
public sealed class NaturalStringComparer : IComparer<string>
{
public int Compare(string a, string b)
{
return SafeNativeMethods.StrCmpLogicalW(a, b);
}
}
public sealed class NaturalFileInfoNameComparer : IComparer<FileInfo>
{
public int Compare(FileInfo a, FileInfo b)
{
return SafeNativeMethods.StrCmpLogicalW(a.Name, b.Name);
}
}

Just thought I'd add to this (with the most concise solution I could find):
public static IOrderedEnumerable<T> OrderByAlphaNumeric<T>(this IEnumerable<T> source, Func<T, string> selector)
{
int max = source
.SelectMany(i => Regex.Matches(selector(i), #"\d+").Cast<Match>().Select(m => (int?)m.Value.Length))
.Max() ?? 0;
return source.OrderBy(i => Regex.Replace(selector(i), #"\d+", m => m.Value.PadLeft(max, '0')));
}
The above pads any numbers in the string to the max length of all numbers in all strings and uses the resulting string to sort.
The cast to (int?) is to allow for collections of strings without any numbers (.Max() on an empty enumerable throws an InvalidOperationException).

None of the existing implementations looked great so I wrote my own. The results are almost identical to the sorting used by modern versions of Windows Explorer (Windows 7/8). The only differences I've seen are 1) although Windows used to (e.g. XP) handle numbers of any length, it's now limited to 19 digits - mine is unlimited, 2) Windows gives inconsistent results with certain sets of Unicode digits - mine works fine (although it doesn't numerically compare digits from surrogate pairs; nor does Windows), and 3) mine can't distinguish different types of non-primary sort weights if they occur in different sections (e.g. "e-1é" vs "é1e-" - the sections before and after the number have diacritic and punctuation weight differences).
public static int CompareNatural(string strA, string strB) {
return CompareNatural(strA, strB, CultureInfo.CurrentCulture, CompareOptions.IgnoreCase);
}
public static int CompareNatural(string strA, string strB, CultureInfo culture, CompareOptions options) {
CompareInfo cmp = culture.CompareInfo;
int iA = 0;
int iB = 0;
int softResult = 0;
int softResultWeight = 0;
while (iA < strA.Length && iB < strB.Length) {
bool isDigitA = Char.IsDigit(strA[iA]);
bool isDigitB = Char.IsDigit(strB[iB]);
if (isDigitA != isDigitB) {
return cmp.Compare(strA, iA, strB, iB, options);
}
else if (!isDigitA && !isDigitB) {
int jA = iA + 1;
int jB = iB + 1;
while (jA < strA.Length && !Char.IsDigit(strA[jA])) jA++;
while (jB < strB.Length && !Char.IsDigit(strB[jB])) jB++;
int cmpResult = cmp.Compare(strA, iA, jA - iA, strB, iB, jB - iB, options);
if (cmpResult != 0) {
// Certain strings may be considered different due to "soft" differences that are
// ignored if more significant differences follow, e.g. a hyphen only affects the
// comparison if no other differences follow
string sectionA = strA.Substring(iA, jA - iA);
string sectionB = strB.Substring(iB, jB - iB);
if (cmp.Compare(sectionA + "1", sectionB + "2", options) ==
cmp.Compare(sectionA + "2", sectionB + "1", options))
{
return cmp.Compare(strA, iA, strB, iB, options);
}
else if (softResultWeight < 1) {
softResult = cmpResult;
softResultWeight = 1;
}
}
iA = jA;
iB = jB;
}
else {
char zeroA = (char)(strA[iA] - (int)Char.GetNumericValue(strA[iA]));
char zeroB = (char)(strB[iB] - (int)Char.GetNumericValue(strB[iB]));
int jA = iA;
int jB = iB;
while (jA < strA.Length && strA[jA] == zeroA) jA++;
while (jB < strB.Length && strB[jB] == zeroB) jB++;
int resultIfSameLength = 0;
do {
isDigitA = jA < strA.Length && Char.IsDigit(strA[jA]);
isDigitB = jB < strB.Length && Char.IsDigit(strB[jB]);
int numA = isDigitA ? (int)Char.GetNumericValue(strA[jA]) : 0;
int numB = isDigitB ? (int)Char.GetNumericValue(strB[jB]) : 0;
if (isDigitA && (char)(strA[jA] - numA) != zeroA) isDigitA = false;
if (isDigitB && (char)(strB[jB] - numB) != zeroB) isDigitB = false;
if (isDigitA && isDigitB) {
if (numA != numB && resultIfSameLength == 0) {
resultIfSameLength = numA < numB ? -1 : 1;
}
jA++;
jB++;
}
}
while (isDigitA && isDigitB);
if (isDigitA != isDigitB) {
// One number has more digits than the other (ignoring leading zeros) - the longer
// number must be larger
return isDigitA ? 1 : -1;
}
else if (resultIfSameLength != 0) {
// Both numbers are the same length (ignoring leading zeros) and at least one of
// the digits differed - the first difference determines the result
return resultIfSameLength;
}
int lA = jA - iA;
int lB = jB - iB;
if (lA != lB) {
// Both numbers are equivalent but one has more leading zeros
return lA > lB ? -1 : 1;
}
else if (zeroA != zeroB && softResultWeight < 2) {
softResult = cmp.Compare(strA, iA, 1, strB, iB, 1, options);
softResultWeight = 2;
}
iA = jA;
iB = jB;
}
}
if (iA < strA.Length || iB < strB.Length) {
return iA < strA.Length ? 1 : -1;
}
else if (softResult != 0) {
return softResult;
}
return 0;
}
The signature matches the Comparison<string> delegate:
string[] files = Directory.GetFiles(#"C:\");
Array.Sort(files, CompareNatural);
Here's a wrapper class for use as IComparer<string>:
public class CustomComparer<T> : IComparer<T> {
private Comparison<T> _comparison;
public CustomComparer(Comparison<T> comparison) {
_comparison = comparison;
}
public int Compare(T x, T y) {
return _comparison(x, y);
}
}
Example:
string[] files = Directory.EnumerateFiles(#"C:\")
.OrderBy(f => f, new CustomComparer<string>(CompareNatural))
.ToArray();
Here's a good set of filenames I use for testing:
Func<string, string> expand = (s) => { int o; while ((o = s.IndexOf('\\')) != -1) { int p = o + 1;
int z = 1; while (s[p] == '0') { z++; p++; } int c = Int32.Parse(s.Substring(p, z));
s = s.Substring(0, o) + new string(s[o - 1], c) + s.Substring(p + z); } return s; };
string encodedFileNames =
"KDEqLW4xMiotbjEzKjAwMDFcMDY2KjAwMlwwMTcqMDA5XDAxNyowMlwwMTcqMDlcMDE3KjEhKjEtISox" +
"LWEqMS4yNT8xLjI1KjEuNT8xLjUqMSoxXDAxNyoxXDAxOCoxXDAxOSoxXDA2NioxXDA2NyoxYSoyXDAx" +
"NyoyXDAxOCo5XDAxNyo5XDAxOCo5XDA2Nio9MSphMDAxdGVzdDAxKmEwMDF0ZXN0aW5nYTBcMzEqYTAw" +
"Mj9hMDAyIGE/YTAwMiBhKmEwMDIqYTAwMmE/YTAwMmEqYTAxdGVzdGluZ2EwMDEqYTAxdnNmcyphMSph" +
"MWEqYTF6KmEyKmIwMDAzcTYqYjAwM3E0KmIwM3E1KmMtZSpjZCpjZipmIDEqZipnP2cgMT9oLW4qaG8t" +
"bipJKmljZS1jcmVhbT9pY2VjcmVhbT9pY2VjcmVhbS0/ajBcNDE/ajAwMWE/ajAxP2shKmsnKmstKmsx" +
"KmthKmxpc3QqbTAwMDNhMDA1YSptMDAzYTAwMDVhKm0wMDNhMDA1Km0wMDNhMDA1YSpuMTIqbjEzKm8t" +
"bjAxMypvLW4xMipvLW40P28tbjQhP28tbjR6P28tbjlhLWI1Km8tbjlhYjUqb24wMTMqb24xMipvbjQ/" +
"b240IT9vbjR6P29uOWEtYjUqb245YWI1Km/CrW4wMTMqb8KtbjEyKnAwMCpwMDEqcDAxwr0hKnAwMcK9" +
"KnAwMcK9YSpwMDHCvcK+KnAwMipwMMK9KnEtbjAxMypxLW4xMipxbjAxMypxbjEyKnItMDAhKnItMDAh" +
"NSpyLTAwIe+8lSpyLTAwYSpyLe+8kFwxIS01KnIt77yQXDEhLe+8lSpyLe+8kFwxISpyLe+8kFwxITUq" +
"ci3vvJBcMSHvvJUqci3vvJBcMWEqci3vvJBcMyE1KnIwMCEqcjAwLTUqcjAwLjUqcjAwNSpyMDBhKnIw" +
"NSpyMDYqcjQqcjUqctmg2aYqctmkKnLZpSpy27Dbtipy27Qqctu1KnLfgN+GKnLfhCpy34UqcuClpuCl" +
"rCpy4KWqKnLgpasqcuCnpuCnrCpy4KeqKnLgp6sqcuCppuCprCpy4KmqKnLgqasqcuCrpuCrrCpy4Kuq" +
"KnLgq6sqcuCtpuCtrCpy4K2qKnLgrasqcuCvpuCvrCpy4K+qKnLgr6sqcuCxpuCxrCpy4LGqKnLgsasq" +
"cuCzpuCzrCpy4LOqKnLgs6sqcuC1puC1rCpy4LWqKnLgtasqcuC5kOC5lipy4LmUKnLguZUqcuC7kOC7" +
"lipy4LuUKnLgu5UqcuC8oOC8pipy4LykKnLgvKUqcuGBgOGBhipy4YGEKnLhgYUqcuGCkOGClipy4YKU" +
"KnLhgpUqcuGfoOGfpipy4Z+kKnLhn6UqcuGgkOGglipy4aCUKnLhoJUqcuGlhuGljCpy4aWKKnLhpYsq" +
"cuGnkOGnlipy4aeUKnLhp5UqcuGtkOGtlipy4a2UKnLhrZUqcuGusOGutipy4a60KnLhrrUqcuGxgOGx" +
"hipy4bGEKnLhsYUqcuGxkOGxlipy4bGUKnLhsZUqcuqYoFwx6pilKnLqmKDqmKUqcuqYoOqYpipy6pik" +
"KnLqmKUqcuqjkOqjlipy6qOUKnLqo5UqcuqkgOqkhipy6qSEKnLqpIUqcuqpkOqplipy6qmUKnLqqZUq" +
"cvCQkqAqcvCQkqUqcvCdn5gqcvCdn50qcu+8kFwxISpy77yQXDEt77yVKnLvvJBcMS7vvJUqcu+8kFwx" +
"YSpy77yQXDHqmKUqcu+8kFwx77yO77yVKnLvvJBcMe+8lSpy77yQ77yVKnLvvJDvvJYqcu+8lCpy77yV" +
"KnNpKnPEsSp0ZXN02aIqdGVzdNmi2aAqdGVzdNmjKnVBZS0qdWFlKnViZS0qdUJlKnVjZS0xw6kqdWNl" +
"McOpLSp1Y2Uxw6kqdWPDqS0xZSp1Y8OpMWUtKnVjw6kxZSp3ZWlhMSp3ZWlhMip3ZWlzczEqd2Vpc3My" +
"KndlaXoxKndlaXoyKndlacOfMSp3ZWnDnzIqeSBhMyp5IGE0KnknYTMqeSdhNCp5K2EzKnkrYTQqeS1h" +
"Myp5LWE0KnlhMyp5YTQqej96IDA1MD96IDIxP3ohMjE/ejIwP3oyMj96YTIxP3rCqTIxP1sxKl8xKsKt" +
"bjEyKsKtbjEzKsSwKg==";
string[] fileNames = Encoding.UTF8.GetString(Convert.FromBase64String(encodedFileNames))
.Replace("*", ".txt?").Split(new[] { "?" }, StringSplitOptions.RemoveEmptyEntries)
.Select(n => expand(n)).ToArray();

Matthews Horsleys answer is the fastest method which doesn't change behaviour depending on which version of windows your program is running on. However, it can be even faster by creating the regex once, and using RegexOptions.Compiled. I also added the option of inserting a string comparer so you can ignore case if needed, and improved readability a bit.
public static IEnumerable<T> OrderByNatural<T>(this IEnumerable<T> items, Func<T, string> selector, StringComparer stringComparer = null)
{
var regex = new Regex(#"\d+", RegexOptions.Compiled);
int maxDigits = items
.SelectMany(i => regex.Matches(selector(i)).Cast<Match>().Select(digitChunk => (int?)digitChunk.Value.Length))
.Max() ?? 0;
return items.OrderBy(i => regex.Replace(selector(i), match => match.Value.PadLeft(maxDigits, '0')), stringComparer ?? StringComparer.CurrentCulture);
}
Use by
var sortedEmployees = employees.OrderByNatural(emp => emp.Name);
This takes 450ms to sort 100,000 strings compared to 300ms for the default .net string comparison - pretty fast!

Pure C# solution for linq orderby:
http://zootfroot.blogspot.com/2009/09/natural-sort-compare-with-linq-orderby.html
public class NaturalSortComparer<T> : IComparer<string>, IDisposable
{
private bool isAscending;
public NaturalSortComparer(bool inAscendingOrder = true)
{
this.isAscending = inAscendingOrder;
}
#region IComparer<string> Members
public int Compare(string x, string y)
{
throw new NotImplementedException();
}
#endregion
#region IComparer<string> Members
int IComparer<string>.Compare(string x, string y)
{
if (x == y)
return 0;
string[] x1, y1;
if (!table.TryGetValue(x, out x1))
{
x1 = Regex.Split(x.Replace(" ", ""), "([0-9]+)");
table.Add(x, x1);
}
if (!table.TryGetValue(y, out y1))
{
y1 = Regex.Split(y.Replace(" ", ""), "([0-9]+)");
table.Add(y, y1);
}
int returnVal;
for (int i = 0; i < x1.Length && i < y1.Length; i++)
{
if (x1[i] != y1[i])
{
returnVal = PartCompare(x1[i], y1[i]);
return isAscending ? returnVal : -returnVal;
}
}
if (y1.Length > x1.Length)
{
returnVal = 1;
}
else if (x1.Length > y1.Length)
{
returnVal = -1;
}
else
{
returnVal = 0;
}
return isAscending ? returnVal : -returnVal;
}
private static int PartCompare(string left, string right)
{
int x, y;
if (!int.TryParse(left, out x))
return left.CompareTo(right);
if (!int.TryParse(right, out y))
return left.CompareTo(right);
return x.CompareTo(y);
}
#endregion
private Dictionary<string, string[]> table = new Dictionary<string, string[]>();
public void Dispose()
{
table.Clear();
table = null;
}
}

My solution:
void Main()
{
new[] {"a4","a3","a2","a10","b5","b4","b400","1","C1d","c1d2"}.OrderBy(x => x, new NaturalStringComparer()).Dump();
}
public class NaturalStringComparer : IComparer<string>
{
private static readonly Regex _re = new Regex(#"(?<=\D)(?=\d)|(?<=\d)(?=\D)", RegexOptions.Compiled);
public int Compare(string x, string y)
{
x = x.ToLower();
y = y.ToLower();
if(string.Compare(x, 0, y, 0, Math.Min(x.Length, y.Length)) == 0)
{
if(x.Length == y.Length) return 0;
return x.Length < y.Length ? -1 : 1;
}
var a = _re.Split(x);
var b = _re.Split(y);
int i = 0;
while(true)
{
int r = PartCompare(a[i], b[i]);
if(r != 0) return r;
++i;
}
}
private static int PartCompare(string x, string y)
{
int a, b;
if(int.TryParse(x, out a) && int.TryParse(y, out b))
return a.CompareTo(b);
return x.CompareTo(y);
}
}
Results:
1
a2
a3
a4
a10
b4
b5
b400
C1d
c1d2

You do need to be careful -- I vaguely recall reading that StrCmpLogicalW, or something like it, was not strictly transitive, and I have observed .NET's sort methods to sometimes get stuck in infinite loops if the comparison function breaks that rule.
A transitive comparison will always report that a < c if a < b and b < c. There exists a function that does a natural sort order comparison that does not always meet that criterion, but I can't recall whether it is StrCmpLogicalW or something else.

This is my code to sort a string having both alpha and numeric characters.
First, this extension method:
public static IEnumerable<string> AlphanumericSort(this IEnumerable<string> me)
{
return me.OrderBy(x => Regex.Replace(x, #"\d+", m => m.Value.PadLeft(50, '0')));
}
Then, simply use it anywhere in your code like this:
List<string> test = new List<string>() { "The 1st", "The 12th", "The 2nd" };
test = test.AlphanumericSort();
How does it works ? By replaceing with zeros:
Original | Regex Replace | The | Returned
List | Apply PadLeft | Sorting | List
| | |
"The 1st" | "The 001st" | "The 001st" | "The 1st"
"The 12th" | "The 012th" | "The 002nd" | "The 2nd"
"The 2nd" | "The 002nd" | "The 012th" | "The 12th"
Works with multiples numbers:
Alphabetical Sorting | Alphanumeric Sorting
|
"Page 21, Line 42" | "Page 3, Line 7"
"Page 21, Line 5" | "Page 3, Line 32"
"Page 3, Line 32" | "Page 21, Line 5"
"Page 3, Line 7" | "Page 21, Line 42"
Hope that's will help.

Here's a version for .NET Core 2.1+ / .NET 5.0+, using spans to avoid allocations
public class NaturalSortStringComparer : IComparer<string>
{
public static NaturalSortStringComparer Ordinal { get; } = new NaturalSortStringComparer(StringComparison.Ordinal);
public static NaturalSortStringComparer OrdinalIgnoreCase { get; } = new NaturalSortStringComparer(StringComparison.OrdinalIgnoreCase);
public static NaturalSortStringComparer CurrentCulture { get; } = new NaturalSortStringComparer(StringComparison.CurrentCulture);
public static NaturalSortStringComparer CurrentCultureIgnoreCase { get; } = new NaturalSortStringComparer(StringComparison.CurrentCultureIgnoreCase);
public static NaturalSortStringComparer InvariantCulture { get; } = new NaturalSortStringComparer(StringComparison.InvariantCulture);
public static NaturalSortStringComparer InvariantCultureIgnoreCase { get; } = new NaturalSortStringComparer(StringComparison.InvariantCultureIgnoreCase);
private readonly StringComparison _comparison;
public NaturalSortStringComparer(StringComparison comparison)
{
_comparison = comparison;
}
public int Compare(string x, string y)
{
// Let string.Compare handle the case where x or y is null
if (x is null || y is null)
return string.Compare(x, y, _comparison);
var xSegments = GetSegments(x);
var ySegments = GetSegments(y);
while (xSegments.MoveNext() && ySegments.MoveNext())
{
int cmp;
// If they're both numbers, compare the value
if (xSegments.CurrentIsNumber && ySegments.CurrentIsNumber)
{
var xValue = long.Parse(xSegments.Current);
var yValue = long.Parse(ySegments.Current);
cmp = xValue.CompareTo(yValue);
if (cmp != 0)
return cmp;
}
// If x is a number and y is not, x is "lesser than" y
else if (xSegments.CurrentIsNumber)
{
return -1;
}
// If y is a number and x is not, x is "greater than" y
else if (ySegments.CurrentIsNumber)
{
return 1;
}
// OK, neither are number, compare the segments as text
cmp = xSegments.Current.CompareTo(ySegments.Current, _comparison);
if (cmp != 0)
return cmp;
}
// At this point, either all segments are equal, or one string is shorter than the other
// If x is shorter, it's "lesser than" y
if (x.Length < y.Length)
return -1;
// If x is longer, it's "greater than" y
if (x.Length > y.Length)
return 1;
// If they have the same length, they're equal
return 0;
}
private static StringSegmentEnumerator GetSegments(string s) => new StringSegmentEnumerator(s);
private struct StringSegmentEnumerator
{
private readonly string _s;
private int _start;
private int _length;
public StringSegmentEnumerator(string s)
{
_s = s;
_start = -1;
_length = 0;
CurrentIsNumber = false;
}
public ReadOnlySpan<char> Current => _s.AsSpan(_start, _length);
public bool CurrentIsNumber { get; private set; }
public bool MoveNext()
{
var currentPosition = _start >= 0
? _start + _length
: 0;
if (currentPosition >= _s.Length)
return false;
int start = currentPosition;
bool isFirstCharDigit = Char.IsDigit(_s[currentPosition]);
while (++currentPosition < _s.Length && Char.IsDigit(_s[currentPosition]) == isFirstCharDigit)
{
}
_start = start;
_length = currentPosition - start;
CurrentIsNumber = isFirstCharDigit;
return true;
}
}
}

Adding to Greg Beech's answer (because I've just been searching for that), if you want to use this from Linq you can use the OrderBy that takes an IComparer. E.g.:
var items = new List<MyItem>();
// fill items
var sorted = items.OrderBy(item => item.Name, new NaturalStringComparer());

Here's a relatively simple example that doesn't use P/Invoke and avoids any allocation during execution.
Feel free to use the code from here, or if it's easier there's a NuGet package:
https://www.nuget.org/packages/NaturalSort
https://github.com/drewnoakes/natural-sort
internal sealed class NaturalStringComparer : IComparer<string>
{
public static NaturalStringComparer Instance { get; } = new NaturalStringComparer();
public int Compare(string x, string y)
{
// sort nulls to the start
if (x == null)
return y == null ? 0 : -1;
if (y == null)
return 1;
var ix = 0;
var iy = 0;
while (true)
{
// sort shorter strings to the start
if (ix >= x.Length)
return iy >= y.Length ? 0 : -1;
if (iy >= y.Length)
return 1;
var cx = x[ix];
var cy = y[iy];
int result;
if (char.IsDigit(cx) && char.IsDigit(cy))
result = CompareInteger(x, y, ref ix, ref iy);
else
result = cx.CompareTo(y[iy]);
if (result != 0)
return result;
ix++;
iy++;
}
}
private static int CompareInteger(string x, string y, ref int ix, ref int iy)
{
var lx = GetNumLength(x, ix);
var ly = GetNumLength(y, iy);
// shorter number first (note, doesn't handle leading zeroes)
if (lx != ly)
return lx.CompareTo(ly);
for (var i = 0; i < lx; i++)
{
var result = x[ix++].CompareTo(y[iy++]);
if (result != 0)
return result;
}
return 0;
}
private static int GetNumLength(string s, int i)
{
var length = 0;
while (i < s.Length && char.IsDigit(s[i++]))
length++;
return length;
}
}
It doesn't ignore leading zeroes, so 01 comes after 2.
Corresponding unit test:
public class NumericStringComparerTests
{
[Fact]
public void OrdersCorrectly()
{
AssertEqual("", "");
AssertEqual(null, null);
AssertEqual("Hello", "Hello");
AssertEqual("Hello123", "Hello123");
AssertEqual("123", "123");
AssertEqual("123Hello", "123Hello");
AssertOrdered("", "Hello");
AssertOrdered(null, "Hello");
AssertOrdered("Hello", "Hello1");
AssertOrdered("Hello123", "Hello124");
AssertOrdered("Hello123", "Hello133");
AssertOrdered("Hello123", "Hello223");
AssertOrdered("123", "124");
AssertOrdered("123", "133");
AssertOrdered("123", "223");
AssertOrdered("123", "1234");
AssertOrdered("123", "2345");
AssertOrdered("0", "1");
AssertOrdered("123Hello", "124Hello");
AssertOrdered("123Hello", "133Hello");
AssertOrdered("123Hello", "223Hello");
AssertOrdered("123Hello", "1234Hello");
}
private static void AssertEqual(string x, string y)
{
Assert.Equal(0, NaturalStringComparer.Instance.Compare(x, y));
Assert.Equal(0, NaturalStringComparer.Instance.Compare(y, x));
}
private static void AssertOrdered(string x, string y)
{
Assert.Equal(-1, NaturalStringComparer.Instance.Compare(x, y));
Assert.Equal( 1, NaturalStringComparer.Instance.Compare(y, x));
}
}

I've actually implemented it as an extension method on the StringComparer so that you could do for example:
StringComparer.CurrentCulture.WithNaturalSort() or
StringComparer.OrdinalIgnoreCase.WithNaturalSort().
The resulting IComparer<string> can be used in all places like OrderBy, OrderByDescending, ThenBy, ThenByDescending, SortedSet<string>, etc. And you can still easily tweak case sensitivity, culture, etc.
The implementation is fairly trivial and it should perform quite well even on large sequences.
I've also published it as a tiny NuGet package, so you can just do:
Install-Package NaturalSort.Extension
The code including XML documentation comments and suite of tests is available in the NaturalSort.Extension GitHub repository.
The entire code is this (if you cannot use C# 7 yet, just install the NuGet package):
public static class StringComparerNaturalSortExtension
{
public static IComparer<string> WithNaturalSort(this StringComparer stringComparer) => new NaturalSortComparer(stringComparer);
private class NaturalSortComparer : IComparer<string>
{
public NaturalSortComparer(StringComparer stringComparer)
{
_stringComparer = stringComparer;
}
private readonly StringComparer _stringComparer;
private static readonly Regex NumberSequenceRegex = new Regex(#"(\d+)", RegexOptions.Compiled | RegexOptions.CultureInvariant);
private static string[] Tokenize(string s) => s == null ? new string[] { } : NumberSequenceRegex.Split(s);
private static ulong ParseNumberOrZero(string s) => ulong.TryParse(s, NumberStyles.None, CultureInfo.InvariantCulture, out var result) ? result : 0;
public int Compare(string s1, string s2)
{
var tokens1 = Tokenize(s1);
var tokens2 = Tokenize(s2);
var zipCompare = tokens1.Zip(tokens2, TokenCompare).FirstOrDefault(x => x != 0);
if (zipCompare != 0)
return zipCompare;
var lengthCompare = tokens1.Length.CompareTo(tokens2.Length);
return lengthCompare;
}
private int TokenCompare(string token1, string token2)
{
var number1 = ParseNumberOrZero(token1);
var number2 = ParseNumberOrZero(token2);
var numberCompare = number1.CompareTo(number2);
if (numberCompare != 0)
return numberCompare;
var stringCompare = _stringComparer.Compare(token1, token2);
return stringCompare;
}
}
}

Inspired by Michael Parker's solution, here is an IComparer implementation that you can drop in to any of the linq ordering methods:
private class NaturalStringComparer : IComparer<string>
{
public int Compare(string left, string right)
{
int max = new[] { left, right }
.SelectMany(x => Regex.Matches(x, #"\d+").Cast<Match>().Select(y => (int?)y.Value.Length))
.Max() ?? 0;
var leftPadded = Regex.Replace(left, #"\d+", m => m.Value.PadLeft(max, '0'));
var rightPadded = Regex.Replace(right, #"\d+", m => m.Value.PadLeft(max, '0'));
return string.Compare(leftPadded, rightPadded);
}
}

Here is a naive one-line regex-less LINQ way (borrowed from python):
var alphaStrings = new List<string>() { "10","2","3","4","50","11","100","a12","b12" };
var orderedString = alphaStrings.OrderBy(g => new Tuple<int, string>(g.ToCharArray().All(char.IsDigit)? int.Parse(g) : int.MaxValue, g));
// Order Now: ["2","3","4","10","11","50","100","a12","b12"]

Expanding on a couple of the previous answers and making use of extension methods, I came up with the following that doesn't have the caveats of potential multiple enumerable enumeration, or performance issues concerned with using multiple regex objects, or calling regex needlessly, that being said, it does use ToList(), which can negate the benefits in larger collections.
The selector supports generic typing to allow any delegate to be assigned, the elements in the source collection are mutated by the selector, then converted to strings with ToString().
private static readonly Regex _NaturalOrderExpr = new Regex(#"\d+", RegexOptions.Compiled);
public static IEnumerable<TSource> OrderByNatural<TSource, TKey>(
this IEnumerable<TSource> source, Func<TSource, TKey> selector)
{
int max = 0;
var selection = source.Select(
o =>
{
var v = selector(o);
var s = v != null ? v.ToString() : String.Empty;
if (!String.IsNullOrWhiteSpace(s))
{
var mc = _NaturalOrderExpr.Matches(s);
if (mc.Count > 0)
{
max = Math.Max(max, mc.Cast<Match>().Max(m => m.Value.Length));
}
}
return new
{
Key = o,
Value = s
};
}).ToList();
return
selection.OrderBy(
o =>
String.IsNullOrWhiteSpace(o.Value) ? o.Value : _NaturalOrderExpr.Replace(o.Value, m => m.Value.PadLeft(max, '0')))
.Select(o => o.Key);
}
public static IEnumerable<TSource> OrderByDescendingNatural<TSource, TKey>(
this IEnumerable<TSource> source, Func<TSource, TKey> selector)
{
int max = 0;
var selection = source.Select(
o =>
{
var v = selector(o);
var s = v != null ? v.ToString() : String.Empty;
if (!String.IsNullOrWhiteSpace(s))
{
var mc = _NaturalOrderExpr.Matches(s);
if (mc.Count > 0)
{
max = Math.Max(max, mc.Cast<Match>().Max(m => m.Value.Length));
}
}
return new
{
Key = o,
Value = s
};
}).ToList();
return
selection.OrderByDescending(
o =>
String.IsNullOrWhiteSpace(o.Value) ? o.Value : _NaturalOrderExpr.Replace(o.Value, m => m.Value.PadLeft(max, '0')))
.Select(o => o.Key);
}

A version that's easier to read/maintain.
public class NaturalStringComparer : IComparer<string>
{
public static NaturalStringComparer Instance { get; } = new NaturalStringComparer();
public int Compare(string x, string y) {
const int LeftIsSmaller = -1;
const int RightIsSmaller = 1;
const int Equal = 0;
var leftString = x;
var rightString = y;
var stringComparer = CultureInfo.CurrentCulture.CompareInfo;
int rightIndex;
int leftIndex;
for (leftIndex = 0, rightIndex = 0;
leftIndex < leftString.Length && rightIndex < rightString.Length;
leftIndex++, rightIndex++) {
var leftChar = leftString[leftIndex];
var rightChar = rightString[leftIndex];
var leftIsNumber = char.IsNumber(leftChar);
var rightIsNumber = char.IsNumber(rightChar);
if (!leftIsNumber && !rightIsNumber) {
var result = stringComparer.Compare(leftString, leftIndex, 1, rightString, leftIndex, 1);
if (result != 0) return result;
} else if (leftIsNumber && !rightIsNumber) {
return LeftIsSmaller;
} else if (!leftIsNumber && rightIsNumber) {
return RightIsSmaller;
} else {
var leftNumberLength = NumberLength(leftString, leftIndex, out var leftNumber);
var rightNumberLength = NumberLength(rightString, rightIndex, out var rightNumber);
if (leftNumberLength < rightNumberLength) {
return LeftIsSmaller;
} else if (leftNumberLength > rightNumberLength) {
return RightIsSmaller;
} else {
if(leftNumber < rightNumber) {
return LeftIsSmaller;
} else if(leftNumber > rightNumber) {
return RightIsSmaller;
}
}
}
}
if (leftString.Length < rightString.Length) {
return LeftIsSmaller;
} else if(leftString.Length > rightString.Length) {
return RightIsSmaller;
}
return Equal;
}
public int NumberLength(string str, int offset, out int number) {
if (string.IsNullOrWhiteSpace(str)) throw new ArgumentNullException(nameof(str));
if (offset >= str.Length) throw new ArgumentOutOfRangeException(nameof(offset), offset, "Offset must be less than the length of the string.");
var currentOffset = offset;
var curChar = str[currentOffset];
if (!char.IsNumber(curChar))
throw new ArgumentException($"'{curChar}' is not a number.", nameof(offset));
int length = 1;
var numberString = string.Empty;
for (currentOffset = offset + 1;
currentOffset < str.Length;
currentOffset++, length++) {
curChar = str[currentOffset];
numberString += curChar;
if (!char.IsNumber(curChar)) {
number = int.Parse(numberString);
return length;
}
}
number = int.Parse(numberString);
return length;
}
}

We had a need for a natural sort to deal with text with the following pattern:
"Test 1-1-1 something"
"Test 1-2-3 something"
...
For some reason when I first looked on SO, I didn't find this post and implemented our own. Compared to some of the solutions presented here, while similar in concept, it could have the benefit of maybe being simpler and easier to understand. However, while I did try to look at performance bottlenecks, It is still a much slower implementation than the default OrderBy().
Here is the extension method I implement:
public static class EnumerableExtensions
{
// set up the regex parser once and for all
private static readonly Regex Regex = new Regex(#"\d+|\D+", RegexOptions.Compiled | RegexOptions.Singleline);
// stateless comparer can be built once
private static readonly AggregateComparer Comparer = new AggregateComparer();
public static IEnumerable<T> OrderByNatural<T>(this IEnumerable<T> source, Func<T, string> selector)
{
// first extract string from object using selector
// then extract digit and non-digit groups
Func<T, IEnumerable<IComparable>> splitter =
s => Regex.Matches(selector(s))
.Cast<Match>()
.Select(m => Char.IsDigit(m.Value[0]) ? (IComparable) int.Parse(m.Value) : m.Value);
return source.OrderBy(splitter, Comparer);
}
/// <summary>
/// This comparer will compare two lists of objects against each other
/// </summary>
/// <remarks>Objects in each list are compare to their corresponding elements in the other
/// list until a difference is found.</remarks>
private class AggregateComparer : IComparer<IEnumerable<IComparable>>
{
public int Compare(IEnumerable<IComparable> x, IEnumerable<IComparable> y)
{
return
x.Zip(y, (a, b) => new {a, b}) // walk both lists
.Select(pair => pair.a.CompareTo(pair.b)) // compare each object
.FirstOrDefault(result => result != 0); // until a difference is found
}
}
}
The idea is to split the original strings into blocks of digits and non-digits ("\d+|\D+"). Since this is a potentially expensive task, it is done only once per entry. We then use a comparer of comparable objects (sorry, I can't find a more proper way to say it). It compares each block to its corresponding block in the other string.
I would like feedback on how this could be improved and what the major flaws are. Note that maintainability is important to us at this point and we are not currently using this in extremely large data sets.

Let me explain my problem and how i was able to solve it.
Problem:- Sort files based on FileName from FileInfo objects which are retrieved from a Directory.
Solution:- I selected the file names from FileInfo and trimed the ".png" part of the file name. Now, just do List.Sort(), which sorts the filenames in Natural sorting order. Based on my testing i found that having .png messes up sorting order. Have a look at the below code
var imageNameList = new DirectoryInfo(#"C:\Temp\Images").GetFiles("*.png").Select(x =>x.Name.Substring(0, x.Name.Length - 4)).ToList();
imageNameList.Sort();

Perform Linq Orderby generic list contain integer and string value [duplicate]

Anyone have a good resource or provide a sample of a natural order sort in C# for an FileInfo array? I am implementing the IComparer interface in my sorts.

The easiest thing to do is just P/Invoke the built-in function in Windows, and use it as the comparison function in your IComparer:
[DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
private static extern int StrCmpLogicalW(string psz1, string psz2);
Michael Kaplan has some examples of how this function works here, and the changes that were made for Vista to make it work more intuitively. The plus side of this function is that it will have the same behaviour as the version of Windows it runs on, however this does mean that it differs between versions of Windows so you need to consider whether this is a problem for you.
So a complete implementation would be something like:
[SuppressUnmanagedCodeSecurity]
internal static class SafeNativeMethods
{
[DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
public static extern int StrCmpLogicalW(string psz1, string psz2);
}
public sealed class NaturalStringComparer : IComparer<string>
{
public int Compare(string a, string b)
{
return SafeNativeMethods.StrCmpLogicalW(a, b);
}
}
public sealed class NaturalFileInfoNameComparer : IComparer<FileInfo>
{
public int Compare(FileInfo a, FileInfo b)
{
return SafeNativeMethods.StrCmpLogicalW(a.Name, b.Name);
}
}

Just thought I'd add to this (with the most concise solution I could find):
public static IOrderedEnumerable<T> OrderByAlphaNumeric<T>(this IEnumerable<T> source, Func<T, string> selector)
{
int max = source
.SelectMany(i => Regex.Matches(selector(i), #"\d+").Cast<Match>().Select(m => (int?)m.Value.Length))
.Max() ?? 0;
return source.OrderBy(i => Regex.Replace(selector(i), #"\d+", m => m.Value.PadLeft(max, '0')));
}
The above pads any numbers in the string to the max length of all numbers in all strings and uses the resulting string to sort.
The cast to (int?) is to allow for collections of strings without any numbers (.Max() on an empty enumerable throws an InvalidOperationException).

None of the existing implementations looked great so I wrote my own. The results are almost identical to the sorting used by modern versions of Windows Explorer (Windows 7/8). The only differences I've seen are 1) although Windows used to (e.g. XP) handle numbers of any length, it's now limited to 19 digits - mine is unlimited, 2) Windows gives inconsistent results with certain sets of Unicode digits - mine works fine (although it doesn't numerically compare digits from surrogate pairs; nor does Windows), and 3) mine can't distinguish different types of non-primary sort weights if they occur in different sections (e.g. "e-1é" vs "é1e-" - the sections before and after the number have diacritic and punctuation weight differences).
public static int CompareNatural(string strA, string strB) {
return CompareNatural(strA, strB, CultureInfo.CurrentCulture, CompareOptions.IgnoreCase);
}
public static int CompareNatural(string strA, string strB, CultureInfo culture, CompareOptions options) {
CompareInfo cmp = culture.CompareInfo;
int iA = 0;
int iB = 0;
int softResult = 0;
int softResultWeight = 0;
while (iA < strA.Length && iB < strB.Length) {
bool isDigitA = Char.IsDigit(strA[iA]);
bool isDigitB = Char.IsDigit(strB[iB]);
if (isDigitA != isDigitB) {
return cmp.Compare(strA, iA, strB, iB, options);
}
else if (!isDigitA && !isDigitB) {
int jA = iA + 1;
int jB = iB + 1;
while (jA < strA.Length && !Char.IsDigit(strA[jA])) jA++;
while (jB < strB.Length && !Char.IsDigit(strB[jB])) jB++;
int cmpResult = cmp.Compare(strA, iA, jA - iA, strB, iB, jB - iB, options);
if (cmpResult != 0) {
// Certain strings may be considered different due to "soft" differences that are
// ignored if more significant differences follow, e.g. a hyphen only affects the
// comparison if no other differences follow
string sectionA = strA.Substring(iA, jA - iA);
string sectionB = strB.Substring(iB, jB - iB);
if (cmp.Compare(sectionA + "1", sectionB + "2", options) ==
cmp.Compare(sectionA + "2", sectionB + "1", options))
{
return cmp.Compare(strA, iA, strB, iB, options);
}
else if (softResultWeight < 1) {
softResult = cmpResult;
softResultWeight = 1;
}
}
iA = jA;
iB = jB;
}
else {
char zeroA = (char)(strA[iA] - (int)Char.GetNumericValue(strA[iA]));
char zeroB = (char)(strB[iB] - (int)Char.GetNumericValue(strB[iB]));
int jA = iA;
int jB = iB;
while (jA < strA.Length && strA[jA] == zeroA) jA++;
while (jB < strB.Length && strB[jB] == zeroB) jB++;
int resultIfSameLength = 0;
do {
isDigitA = jA < strA.Length && Char.IsDigit(strA[jA]);
isDigitB = jB < strB.Length && Char.IsDigit(strB[jB]);
int numA = isDigitA ? (int)Char.GetNumericValue(strA[jA]) : 0;
int numB = isDigitB ? (int)Char.GetNumericValue(strB[jB]) : 0;
if (isDigitA && (char)(strA[jA] - numA) != zeroA) isDigitA = false;
if (isDigitB && (char)(strB[jB] - numB) != zeroB) isDigitB = false;
if (isDigitA && isDigitB) {
if (numA != numB && resultIfSameLength == 0) {
resultIfSameLength = numA < numB ? -1 : 1;
}
jA++;
jB++;
}
}
while (isDigitA && isDigitB);
if (isDigitA != isDigitB) {
// One number has more digits than the other (ignoring leading zeros) - the longer
// number must be larger
return isDigitA ? 1 : -1;
}
else if (resultIfSameLength != 0) {
// Both numbers are the same length (ignoring leading zeros) and at least one of
// the digits differed - the first difference determines the result
return resultIfSameLength;
}
int lA = jA - iA;
int lB = jB - iB;
if (lA != lB) {
// Both numbers are equivalent but one has more leading zeros
return lA > lB ? -1 : 1;
}
else if (zeroA != zeroB && softResultWeight < 2) {
softResult = cmp.Compare(strA, iA, 1, strB, iB, 1, options);
softResultWeight = 2;
}
iA = jA;
iB = jB;
}
}
if (iA < strA.Length || iB < strB.Length) {
return iA < strA.Length ? 1 : -1;
}
else if (softResult != 0) {
return softResult;
}
return 0;
}
The signature matches the Comparison<string> delegate:
string[] files = Directory.GetFiles(#"C:\");
Array.Sort(files, CompareNatural);
Here's a wrapper class for use as IComparer<string>:
public class CustomComparer<T> : IComparer<T> {
private Comparison<T> _comparison;
public CustomComparer(Comparison<T> comparison) {
_comparison = comparison;
}
public int Compare(T x, T y) {
return _comparison(x, y);
}
}
Example:
string[] files = Directory.EnumerateFiles(#"C:\")
.OrderBy(f => f, new CustomComparer<string>(CompareNatural))
.ToArray();
Here's a good set of filenames I use for testing:
Func<string, string> expand = (s) => { int o; while ((o = s.IndexOf('\\')) != -1) { int p = o + 1;
int z = 1; while (s[p] == '0') { z++; p++; } int c = Int32.Parse(s.Substring(p, z));
s = s.Substring(0, o) + new string(s[o - 1], c) + s.Substring(p + z); } return s; };
string encodedFileNames =
"KDEqLW4xMiotbjEzKjAwMDFcMDY2KjAwMlwwMTcqMDA5XDAxNyowMlwwMTcqMDlcMDE3KjEhKjEtISox" +
"LWEqMS4yNT8xLjI1KjEuNT8xLjUqMSoxXDAxNyoxXDAxOCoxXDAxOSoxXDA2NioxXDA2NyoxYSoyXDAx" +
"NyoyXDAxOCo5XDAxNyo5XDAxOCo5XDA2Nio9MSphMDAxdGVzdDAxKmEwMDF0ZXN0aW5nYTBcMzEqYTAw" +
"Mj9hMDAyIGE/YTAwMiBhKmEwMDIqYTAwMmE/YTAwMmEqYTAxdGVzdGluZ2EwMDEqYTAxdnNmcyphMSph" +
"MWEqYTF6KmEyKmIwMDAzcTYqYjAwM3E0KmIwM3E1KmMtZSpjZCpjZipmIDEqZipnP2cgMT9oLW4qaG8t" +
"bipJKmljZS1jcmVhbT9pY2VjcmVhbT9pY2VjcmVhbS0/ajBcNDE/ajAwMWE/ajAxP2shKmsnKmstKmsx" +
"KmthKmxpc3QqbTAwMDNhMDA1YSptMDAzYTAwMDVhKm0wMDNhMDA1Km0wMDNhMDA1YSpuMTIqbjEzKm8t" +
"bjAxMypvLW4xMipvLW40P28tbjQhP28tbjR6P28tbjlhLWI1Km8tbjlhYjUqb24wMTMqb24xMipvbjQ/" +
"b240IT9vbjR6P29uOWEtYjUqb245YWI1Km/CrW4wMTMqb8KtbjEyKnAwMCpwMDEqcDAxwr0hKnAwMcK9" +
"KnAwMcK9YSpwMDHCvcK+KnAwMipwMMK9KnEtbjAxMypxLW4xMipxbjAxMypxbjEyKnItMDAhKnItMDAh" +
"NSpyLTAwIe+8lSpyLTAwYSpyLe+8kFwxIS01KnIt77yQXDEhLe+8lSpyLe+8kFwxISpyLe+8kFwxITUq" +
"ci3vvJBcMSHvvJUqci3vvJBcMWEqci3vvJBcMyE1KnIwMCEqcjAwLTUqcjAwLjUqcjAwNSpyMDBhKnIw" +
"NSpyMDYqcjQqcjUqctmg2aYqctmkKnLZpSpy27Dbtipy27Qqctu1KnLfgN+GKnLfhCpy34UqcuClpuCl" +
"rCpy4KWqKnLgpasqcuCnpuCnrCpy4KeqKnLgp6sqcuCppuCprCpy4KmqKnLgqasqcuCrpuCrrCpy4Kuq" +
"KnLgq6sqcuCtpuCtrCpy4K2qKnLgrasqcuCvpuCvrCpy4K+qKnLgr6sqcuCxpuCxrCpy4LGqKnLgsasq" +
"cuCzpuCzrCpy4LOqKnLgs6sqcuC1puC1rCpy4LWqKnLgtasqcuC5kOC5lipy4LmUKnLguZUqcuC7kOC7" +
"lipy4LuUKnLgu5UqcuC8oOC8pipy4LykKnLgvKUqcuGBgOGBhipy4YGEKnLhgYUqcuGCkOGClipy4YKU" +
"KnLhgpUqcuGfoOGfpipy4Z+kKnLhn6UqcuGgkOGglipy4aCUKnLhoJUqcuGlhuGljCpy4aWKKnLhpYsq" +
"cuGnkOGnlipy4aeUKnLhp5UqcuGtkOGtlipy4a2UKnLhrZUqcuGusOGutipy4a60KnLhrrUqcuGxgOGx" +
"hipy4bGEKnLhsYUqcuGxkOGxlipy4bGUKnLhsZUqcuqYoFwx6pilKnLqmKDqmKUqcuqYoOqYpipy6pik" +
"KnLqmKUqcuqjkOqjlipy6qOUKnLqo5UqcuqkgOqkhipy6qSEKnLqpIUqcuqpkOqplipy6qmUKnLqqZUq" +
"cvCQkqAqcvCQkqUqcvCdn5gqcvCdn50qcu+8kFwxISpy77yQXDEt77yVKnLvvJBcMS7vvJUqcu+8kFwx" +
"YSpy77yQXDHqmKUqcu+8kFwx77yO77yVKnLvvJBcMe+8lSpy77yQ77yVKnLvvJDvvJYqcu+8lCpy77yV" +
"KnNpKnPEsSp0ZXN02aIqdGVzdNmi2aAqdGVzdNmjKnVBZS0qdWFlKnViZS0qdUJlKnVjZS0xw6kqdWNl" +
"McOpLSp1Y2Uxw6kqdWPDqS0xZSp1Y8OpMWUtKnVjw6kxZSp3ZWlhMSp3ZWlhMip3ZWlzczEqd2Vpc3My" +
"KndlaXoxKndlaXoyKndlacOfMSp3ZWnDnzIqeSBhMyp5IGE0KnknYTMqeSdhNCp5K2EzKnkrYTQqeS1h" +
"Myp5LWE0KnlhMyp5YTQqej96IDA1MD96IDIxP3ohMjE/ejIwP3oyMj96YTIxP3rCqTIxP1sxKl8xKsKt" +
"bjEyKsKtbjEzKsSwKg==";
string[] fileNames = Encoding.UTF8.GetString(Convert.FromBase64String(encodedFileNames))
.Replace("*", ".txt?").Split(new[] { "?" }, StringSplitOptions.RemoveEmptyEntries)
.Select(n => expand(n)).ToArray();

Matthews Horsleys answer is the fastest method which doesn't change behaviour depending on which version of windows your program is running on. However, it can be even faster by creating the regex once, and using RegexOptions.Compiled. I also added the option of inserting a string comparer so you can ignore case if needed, and improved readability a bit.
public static IEnumerable<T> OrderByNatural<T>(this IEnumerable<T> items, Func<T, string> selector, StringComparer stringComparer = null)
{
var regex = new Regex(#"\d+", RegexOptions.Compiled);
int maxDigits = items
.SelectMany(i => regex.Matches(selector(i)).Cast<Match>().Select(digitChunk => (int?)digitChunk.Value.Length))
.Max() ?? 0;
return items.OrderBy(i => regex.Replace(selector(i), match => match.Value.PadLeft(maxDigits, '0')), stringComparer ?? StringComparer.CurrentCulture);
}
Use by
var sortedEmployees = employees.OrderByNatural(emp => emp.Name);
This takes 450ms to sort 100,000 strings compared to 300ms for the default .net string comparison - pretty fast!

Pure C# solution for linq orderby:
http://zootfroot.blogspot.com/2009/09/natural-sort-compare-with-linq-orderby.html
public class NaturalSortComparer<T> : IComparer<string>, IDisposable
{
private bool isAscending;
public NaturalSortComparer(bool inAscendingOrder = true)
{
this.isAscending = inAscendingOrder;
}
#region IComparer<string> Members
public int Compare(string x, string y)
{
throw new NotImplementedException();
}
#endregion
#region IComparer<string> Members
int IComparer<string>.Compare(string x, string y)
{
if (x == y)
return 0;
string[] x1, y1;
if (!table.TryGetValue(x, out x1))
{
x1 = Regex.Split(x.Replace(" ", ""), "([0-9]+)");
table.Add(x, x1);
}
if (!table.TryGetValue(y, out y1))
{
y1 = Regex.Split(y.Replace(" ", ""), "([0-9]+)");
table.Add(y, y1);
}
int returnVal;
for (int i = 0; i < x1.Length && i < y1.Length; i++)
{
if (x1[i] != y1[i])
{
returnVal = PartCompare(x1[i], y1[i]);
return isAscending ? returnVal : -returnVal;
}
}
if (y1.Length > x1.Length)
{
returnVal = 1;
}
else if (x1.Length > y1.Length)
{
returnVal = -1;
}
else
{
returnVal = 0;
}
return isAscending ? returnVal : -returnVal;
}
private static int PartCompare(string left, string right)
{
int x, y;
if (!int.TryParse(left, out x))
return left.CompareTo(right);
if (!int.TryParse(right, out y))
return left.CompareTo(right);
return x.CompareTo(y);
}
#endregion
private Dictionary<string, string[]> table = new Dictionary<string, string[]>();
public void Dispose()
{
table.Clear();
table = null;
}
}

My solution:
void Main()
{
new[] {"a4","a3","a2","a10","b5","b4","b400","1","C1d","c1d2"}.OrderBy(x => x, new NaturalStringComparer()).Dump();
}
public class NaturalStringComparer : IComparer<string>
{
private static readonly Regex _re = new Regex(#"(?<=\D)(?=\d)|(?<=\d)(?=\D)", RegexOptions.Compiled);
public int Compare(string x, string y)
{
x = x.ToLower();
y = y.ToLower();
if(string.Compare(x, 0, y, 0, Math.Min(x.Length, y.Length)) == 0)
{
if(x.Length == y.Length) return 0;
return x.Length < y.Length ? -1 : 1;
}
var a = _re.Split(x);
var b = _re.Split(y);
int i = 0;
while(true)
{
int r = PartCompare(a[i], b[i]);
if(r != 0) return r;
++i;
}
}
private static int PartCompare(string x, string y)
{
int a, b;
if(int.TryParse(x, out a) && int.TryParse(y, out b))
return a.CompareTo(b);
return x.CompareTo(y);
}
}
Results:
1
a2
a3
a4
a10
b4
b5
b400
C1d
c1d2

You do need to be careful -- I vaguely recall reading that StrCmpLogicalW, or something like it, was not strictly transitive, and I have observed .NET's sort methods to sometimes get stuck in infinite loops if the comparison function breaks that rule.
A transitive comparison will always report that a < c if a < b and b < c. There exists a function that does a natural sort order comparison that does not always meet that criterion, but I can't recall whether it is StrCmpLogicalW or something else.

This is my code to sort a string having both alpha and numeric characters.
First, this extension method:
public static IEnumerable<string> AlphanumericSort(this IEnumerable<string> me)
{
return me.OrderBy(x => Regex.Replace(x, #"\d+", m => m.Value.PadLeft(50, '0')));
}
Then, simply use it anywhere in your code like this:
List<string> test = new List<string>() { "The 1st", "The 12th", "The 2nd" };
test = test.AlphanumericSort();
How does it works ? By replaceing with zeros:
Original | Regex Replace | The | Returned
List | Apply PadLeft | Sorting | List
| | |
"The 1st" | "The 001st" | "The 001st" | "The 1st"
"The 12th" | "The 012th" | "The 002nd" | "The 2nd"
"The 2nd" | "The 002nd" | "The 012th" | "The 12th"
Works with multiples numbers:
Alphabetical Sorting | Alphanumeric Sorting
|
"Page 21, Line 42" | "Page 3, Line 7"
"Page 21, Line 5" | "Page 3, Line 32"
"Page 3, Line 32" | "Page 21, Line 5"
"Page 3, Line 7" | "Page 21, Line 42"
Hope that's will help.

Here's a version for .NET Core 2.1+ / .NET 5.0+, using spans to avoid allocations
public class NaturalSortStringComparer : IComparer<string>
{
public static NaturalSortStringComparer Ordinal { get; } = new NaturalSortStringComparer(StringComparison.Ordinal);
public static NaturalSortStringComparer OrdinalIgnoreCase { get; } = new NaturalSortStringComparer(StringComparison.OrdinalIgnoreCase);
public static NaturalSortStringComparer CurrentCulture { get; } = new NaturalSortStringComparer(StringComparison.CurrentCulture);
public static NaturalSortStringComparer CurrentCultureIgnoreCase { get; } = new NaturalSortStringComparer(StringComparison.CurrentCultureIgnoreCase);
public static NaturalSortStringComparer InvariantCulture { get; } = new NaturalSortStringComparer(StringComparison.InvariantCulture);
public static NaturalSortStringComparer InvariantCultureIgnoreCase { get; } = new NaturalSortStringComparer(StringComparison.InvariantCultureIgnoreCase);
private readonly StringComparison _comparison;
public NaturalSortStringComparer(StringComparison comparison)
{
_comparison = comparison;
}
public int Compare(string x, string y)
{
// Let string.Compare handle the case where x or y is null
if (x is null || y is null)
return string.Compare(x, y, _comparison);
var xSegments = GetSegments(x);
var ySegments = GetSegments(y);
while (xSegments.MoveNext() && ySegments.MoveNext())
{
int cmp;
// If they're both numbers, compare the value
if (xSegments.CurrentIsNumber && ySegments.CurrentIsNumber)
{
var xValue = long.Parse(xSegments.Current);
var yValue = long.Parse(ySegments.Current);
cmp = xValue.CompareTo(yValue);
if (cmp != 0)
return cmp;
}
// If x is a number and y is not, x is "lesser than" y
else if (xSegments.CurrentIsNumber)
{
return -1;
}
// If y is a number and x is not, x is "greater than" y
else if (ySegments.CurrentIsNumber)
{
return 1;
}
// OK, neither are number, compare the segments as text
cmp = xSegments.Current.CompareTo(ySegments.Current, _comparison);
if (cmp != 0)
return cmp;
}
// At this point, either all segments are equal, or one string is shorter than the other
// If x is shorter, it's "lesser than" y
if (x.Length < y.Length)
return -1;
// If x is longer, it's "greater than" y
if (x.Length > y.Length)
return 1;
// If they have the same length, they're equal
return 0;
}
private static StringSegmentEnumerator GetSegments(string s) => new StringSegmentEnumerator(s);
private struct StringSegmentEnumerator
{
private readonly string _s;
private int _start;
private int _length;
public StringSegmentEnumerator(string s)
{
_s = s;
_start = -1;
_length = 0;
CurrentIsNumber = false;
}
public ReadOnlySpan<char> Current => _s.AsSpan(_start, _length);
public bool CurrentIsNumber { get; private set; }
public bool MoveNext()
{
var currentPosition = _start >= 0
? _start + _length
: 0;
if (currentPosition >= _s.Length)
return false;
int start = currentPosition;
bool isFirstCharDigit = Char.IsDigit(_s[currentPosition]);
while (++currentPosition < _s.Length && Char.IsDigit(_s[currentPosition]) == isFirstCharDigit)
{
}
_start = start;
_length = currentPosition - start;
CurrentIsNumber = isFirstCharDigit;
return true;
}
}
}

Adding to Greg Beech's answer (because I've just been searching for that), if you want to use this from Linq you can use the OrderBy that takes an IComparer. E.g.:
var items = new List<MyItem>();
// fill items
var sorted = items.OrderBy(item => item.Name, new NaturalStringComparer());

Here's a relatively simple example that doesn't use P/Invoke and avoids any allocation during execution.
Feel free to use the code from here, or if it's easier there's a NuGet package:
https://www.nuget.org/packages/NaturalSort
https://github.com/drewnoakes/natural-sort
internal sealed class NaturalStringComparer : IComparer<string>
{
public static NaturalStringComparer Instance { get; } = new NaturalStringComparer();
public int Compare(string x, string y)
{
// sort nulls to the start
if (x == null)
return y == null ? 0 : -1;
if (y == null)
return 1;
var ix = 0;
var iy = 0;
while (true)
{
// sort shorter strings to the start
if (ix >= x.Length)
return iy >= y.Length ? 0 : -1;
if (iy >= y.Length)
return 1;
var cx = x[ix];
var cy = y[iy];
int result;
if (char.IsDigit(cx) && char.IsDigit(cy))
result = CompareInteger(x, y, ref ix, ref iy);
else
result = cx.CompareTo(y[iy]);
if (result != 0)
return result;
ix++;
iy++;
}
}
private static int CompareInteger(string x, string y, ref int ix, ref int iy)
{
var lx = GetNumLength(x, ix);
var ly = GetNumLength(y, iy);
// shorter number first (note, doesn't handle leading zeroes)
if (lx != ly)
return lx.CompareTo(ly);
for (var i = 0; i < lx; i++)
{
var result = x[ix++].CompareTo(y[iy++]);
if (result != 0)
return result;
}
return 0;
}
private static int GetNumLength(string s, int i)
{
var length = 0;
while (i < s.Length && char.IsDigit(s[i++]))
length++;
return length;
}
}
It doesn't ignore leading zeroes, so 01 comes after 2.
Corresponding unit test:
public class NumericStringComparerTests
{
[Fact]
public void OrdersCorrectly()
{
AssertEqual("", "");
AssertEqual(null, null);
AssertEqual("Hello", "Hello");
AssertEqual("Hello123", "Hello123");
AssertEqual("123", "123");
AssertEqual("123Hello", "123Hello");
AssertOrdered("", "Hello");
AssertOrdered(null, "Hello");
AssertOrdered("Hello", "Hello1");
AssertOrdered("Hello123", "Hello124");
AssertOrdered("Hello123", "Hello133");
AssertOrdered("Hello123", "Hello223");
AssertOrdered("123", "124");
AssertOrdered("123", "133");
AssertOrdered("123", "223");
AssertOrdered("123", "1234");
AssertOrdered("123", "2345");
AssertOrdered("0", "1");
AssertOrdered("123Hello", "124Hello");
AssertOrdered("123Hello", "133Hello");
AssertOrdered("123Hello", "223Hello");
AssertOrdered("123Hello", "1234Hello");
}
private static void AssertEqual(string x, string y)
{
Assert.Equal(0, NaturalStringComparer.Instance.Compare(x, y));
Assert.Equal(0, NaturalStringComparer.Instance.Compare(y, x));
}
private static void AssertOrdered(string x, string y)
{
Assert.Equal(-1, NaturalStringComparer.Instance.Compare(x, y));
Assert.Equal( 1, NaturalStringComparer.Instance.Compare(y, x));
}
}

I've actually implemented it as an extension method on the StringComparer so that you could do for example:
StringComparer.CurrentCulture.WithNaturalSort() or
StringComparer.OrdinalIgnoreCase.WithNaturalSort().
The resulting IComparer<string> can be used in all places like OrderBy, OrderByDescending, ThenBy, ThenByDescending, SortedSet<string>, etc. And you can still easily tweak case sensitivity, culture, etc.
The implementation is fairly trivial and it should perform quite well even on large sequences.
I've also published it as a tiny NuGet package, so you can just do:
Install-Package NaturalSort.Extension
The code including XML documentation comments and suite of tests is available in the NaturalSort.Extension GitHub repository.
The entire code is this (if you cannot use C# 7 yet, just install the NuGet package):
public static class StringComparerNaturalSortExtension
{
public static IComparer<string> WithNaturalSort(this StringComparer stringComparer) => new NaturalSortComparer(stringComparer);
private class NaturalSortComparer : IComparer<string>
{
public NaturalSortComparer(StringComparer stringComparer)
{
_stringComparer = stringComparer;
}
private readonly StringComparer _stringComparer;
private static readonly Regex NumberSequenceRegex = new Regex(#"(\d+)", RegexOptions.Compiled | RegexOptions.CultureInvariant);
private static string[] Tokenize(string s) => s == null ? new string[] { } : NumberSequenceRegex.Split(s);
private static ulong ParseNumberOrZero(string s) => ulong.TryParse(s, NumberStyles.None, CultureInfo.InvariantCulture, out var result) ? result : 0;
public int Compare(string s1, string s2)
{
var tokens1 = Tokenize(s1);
var tokens2 = Tokenize(s2);
var zipCompare = tokens1.Zip(tokens2, TokenCompare).FirstOrDefault(x => x != 0);
if (zipCompare != 0)
return zipCompare;
var lengthCompare = tokens1.Length.CompareTo(tokens2.Length);
return lengthCompare;
}
private int TokenCompare(string token1, string token2)
{
var number1 = ParseNumberOrZero(token1);
var number2 = ParseNumberOrZero(token2);
var numberCompare = number1.CompareTo(number2);
if (numberCompare != 0)
return numberCompare;
var stringCompare = _stringComparer.Compare(token1, token2);
return stringCompare;
}
}
}

Inspired by Michael Parker's solution, here is an IComparer implementation that you can drop in to any of the linq ordering methods:
private class NaturalStringComparer : IComparer<string>
{
public int Compare(string left, string right)
{
int max = new[] { left, right }
.SelectMany(x => Regex.Matches(x, #"\d+").Cast<Match>().Select(y => (int?)y.Value.Length))
.Max() ?? 0;
var leftPadded = Regex.Replace(left, #"\d+", m => m.Value.PadLeft(max, '0'));
var rightPadded = Regex.Replace(right, #"\d+", m => m.Value.PadLeft(max, '0'));
return string.Compare(leftPadded, rightPadded);
}
}

Here is a naive one-line regex-less LINQ way (borrowed from python):
var alphaStrings = new List<string>() { "10","2","3","4","50","11","100","a12","b12" };
var orderedString = alphaStrings.OrderBy(g => new Tuple<int, string>(g.ToCharArray().All(char.IsDigit)? int.Parse(g) : int.MaxValue, g));
// Order Now: ["2","3","4","10","11","50","100","a12","b12"]

Expanding on a couple of the previous answers and making use of extension methods, I came up with the following that doesn't have the caveats of potential multiple enumerable enumeration, or performance issues concerned with using multiple regex objects, or calling regex needlessly, that being said, it does use ToList(), which can negate the benefits in larger collections.
The selector supports generic typing to allow any delegate to be assigned, the elements in the source collection are mutated by the selector, then converted to strings with ToString().
private static readonly Regex _NaturalOrderExpr = new Regex(#"\d+", RegexOptions.Compiled);
public static IEnumerable<TSource> OrderByNatural<TSource, TKey>(
this IEnumerable<TSource> source, Func<TSource, TKey> selector)
{
int max = 0;
var selection = source.Select(
o =>
{
var v = selector(o);
var s = v != null ? v.ToString() : String.Empty;
if (!String.IsNullOrWhiteSpace(s))
{
var mc = _NaturalOrderExpr.Matches(s);
if (mc.Count > 0)
{
max = Math.Max(max, mc.Cast<Match>().Max(m => m.Value.Length));
}
}
return new
{
Key = o,
Value = s
};
}).ToList();
return
selection.OrderBy(
o =>
String.IsNullOrWhiteSpace(o.Value) ? o.Value : _NaturalOrderExpr.Replace(o.Value, m => m.Value.PadLeft(max, '0')))
.Select(o => o.Key);
}
public static IEnumerable<TSource> OrderByDescendingNatural<TSource, TKey>(
this IEnumerable<TSource> source, Func<TSource, TKey> selector)
{
int max = 0;
var selection = source.Select(
o =>
{
var v = selector(o);
var s = v != null ? v.ToString() : String.Empty;
if (!String.IsNullOrWhiteSpace(s))
{
var mc = _NaturalOrderExpr.Matches(s);
if (mc.Count > 0)
{
max = Math.Max(max, mc.Cast<Match>().Max(m => m.Value.Length));
}
}
return new
{
Key = o,
Value = s
};
}).ToList();
return
selection.OrderByDescending(
o =>
String.IsNullOrWhiteSpace(o.Value) ? o.Value : _NaturalOrderExpr.Replace(o.Value, m => m.Value.PadLeft(max, '0')))
.Select(o => o.Key);
}

A version that's easier to read/maintain.
public class NaturalStringComparer : IComparer<string>
{
public static NaturalStringComparer Instance { get; } = new NaturalStringComparer();
public int Compare(string x, string y) {
const int LeftIsSmaller = -1;
const int RightIsSmaller = 1;
const int Equal = 0;
var leftString = x;
var rightString = y;
var stringComparer = CultureInfo.CurrentCulture.CompareInfo;
int rightIndex;
int leftIndex;
for (leftIndex = 0, rightIndex = 0;
leftIndex < leftString.Length && rightIndex < rightString.Length;
leftIndex++, rightIndex++) {
var leftChar = leftString[leftIndex];
var rightChar = rightString[leftIndex];
var leftIsNumber = char.IsNumber(leftChar);
var rightIsNumber = char.IsNumber(rightChar);
if (!leftIsNumber && !rightIsNumber) {
var result = stringComparer.Compare(leftString, leftIndex, 1, rightString, leftIndex, 1);
if (result != 0) return result;
} else if (leftIsNumber && !rightIsNumber) {
return LeftIsSmaller;
} else if (!leftIsNumber && rightIsNumber) {
return RightIsSmaller;
} else {
var leftNumberLength = NumberLength(leftString, leftIndex, out var leftNumber);
var rightNumberLength = NumberLength(rightString, rightIndex, out var rightNumber);
if (leftNumberLength < rightNumberLength) {
return LeftIsSmaller;
} else if (leftNumberLength > rightNumberLength) {
return RightIsSmaller;
} else {
if(leftNumber < rightNumber) {
return LeftIsSmaller;
} else if(leftNumber > rightNumber) {
return RightIsSmaller;
}
}
}
}
if (leftString.Length < rightString.Length) {
return LeftIsSmaller;
} else if(leftString.Length > rightString.Length) {
return RightIsSmaller;
}
return Equal;
}
public int NumberLength(string str, int offset, out int number) {
if (string.IsNullOrWhiteSpace(str)) throw new ArgumentNullException(nameof(str));
if (offset >= str.Length) throw new ArgumentOutOfRangeException(nameof(offset), offset, "Offset must be less than the length of the string.");
var currentOffset = offset;
var curChar = str[currentOffset];
if (!char.IsNumber(curChar))
throw new ArgumentException($"'{curChar}' is not a number.", nameof(offset));
int length = 1;
var numberString = string.Empty;
for (currentOffset = offset + 1;
currentOffset < str.Length;
currentOffset++, length++) {
curChar = str[currentOffset];
numberString += curChar;
if (!char.IsNumber(curChar)) {
number = int.Parse(numberString);
return length;
}
}
number = int.Parse(numberString);
return length;
}
}

We had a need for a natural sort to deal with text with the following pattern:
"Test 1-1-1 something"
"Test 1-2-3 something"
...
For some reason when I first looked on SO, I didn't find this post and implemented our own. Compared to some of the solutions presented here, while similar in concept, it could have the benefit of maybe being simpler and easier to understand. However, while I did try to look at performance bottlenecks, It is still a much slower implementation than the default OrderBy().
Here is the extension method I implement:
public static class EnumerableExtensions
{
// set up the regex parser once and for all
private static readonly Regex Regex = new Regex(#"\d+|\D+", RegexOptions.Compiled | RegexOptions.Singleline);
// stateless comparer can be built once
private static readonly AggregateComparer Comparer = new AggregateComparer();
public static IEnumerable<T> OrderByNatural<T>(this IEnumerable<T> source, Func<T, string> selector)
{
// first extract string from object using selector
// then extract digit and non-digit groups
Func<T, IEnumerable<IComparable>> splitter =
s => Regex.Matches(selector(s))
.Cast<Match>()
.Select(m => Char.IsDigit(m.Value[0]) ? (IComparable) int.Parse(m.Value) : m.Value);
return source.OrderBy(splitter, Comparer);
}
/// <summary>
/// This comparer will compare two lists of objects against each other
/// </summary>
/// <remarks>Objects in each list are compare to their corresponding elements in the other
/// list until a difference is found.</remarks>
private class AggregateComparer : IComparer<IEnumerable<IComparable>>
{
public int Compare(IEnumerable<IComparable> x, IEnumerable<IComparable> y)
{
return
x.Zip(y, (a, b) => new {a, b}) // walk both lists
.Select(pair => pair.a.CompareTo(pair.b)) // compare each object
.FirstOrDefault(result => result != 0); // until a difference is found
}
}
}
The idea is to split the original strings into blocks of digits and non-digits ("\d+|\D+"). Since this is a potentially expensive task, it is done only once per entry. We then use a comparer of comparable objects (sorry, I can't find a more proper way to say it). It compares each block to its corresponding block in the other string.
I would like feedback on how this could be improved and what the major flaws are. Note that maintainability is important to us at this point and we are not currently using this in extremely large data sets.

Let me explain my problem and how i was able to solve it.
Problem:- Sort files based on FileName from FileInfo objects which are retrieved from a Directory.
Solution:- I selected the file names from FileInfo and trimed the ".png" part of the file name. Now, just do List.Sort(), which sorts the filenames in Natural sorting order. Based on my testing i found that having .png messes up sorting order. Have a look at the below code
var imageNameList = new DirectoryInfo(#"C:\Temp\Images").GetFiles("*.png").Select(x =>x.Name.Substring(0, x.Name.Length - 4)).ToList();
imageNameList.Sort();

Searching for a string in a string

Dear stackoverflow members,
I have this string:
string data = "1Position1234Article4321Quantity2Position4323Article3323Quantity";
I want to search for the values where the "keyword" is Position. In this case I want to get back 1 and 2. Each value is "indexed" with its own "keyword". So the value 1 in this string has the Position seperator. The value 1234 has the Article seperator and the value 4321 has the Quantity seperator.
I need a way to search through the string and want to get all positions, articles and quantitys back. Without the keywords.
Output shout be:
string[] position = {"1", "2"};
string[] article = {"1234", "4323"};
string[] quantity = {"4321", "3323"};
Hopefully some can help me here.
Thanks!

This is q quick solution I've come up with in LinqPad:
void Main()
{
string data = "1Position1234Article4321Quantity2Position4323Article3323Quantity";
var Articles = Indices(data, "Article").Dump("Articles: ");
var Posistions = Indices(data, "Position").Dump("Positions :");
var Quantities = Indices(data, "Quantity").Dump("Quantities :");
}
// Define other methods and classes here
public List<int> Indices(string source, string keyword)
{
var results = new List<int>();
//source: http://stackoverflow.com/questions/3720012/regular-expression-to-split-string-and-number
var temp = Regex.Split(source, "(?<Alpha>[a-zA-Z]*)(?<Numeric>[0-9]*)").ToList().Where (r => !String.IsNullOrEmpty(r)).ToList();
//select the list with index only where key word matches
var indices = temp.Select ((v,i) => new {index = i, value = v})
.Where (t => t.value == keyword);
foreach (var element in indices)
{
int val;
//get previous list entry based on index and parse it
if(Int32.TryParse(temp[element.index -1], out val))
{
results.Add(val);
}
}
return results;
}
Output:

Here's a possible algorithm:
Run trough the list and take each number / keyword.
Put them in a dictionary with key "keyword", value a list with all "numbers".
Iterate the dictionary and print they key + its values.

Below snippet can use to get the output like what you expected.
string data = "1Position1234Article4321Quantity2Position4323Article3323Quantity";
StringBuilder sb = new StringBuilder();
StringBuilder sbWord = new StringBuilder();
bool isDigit = false;
bool isChar = false;
Dictionary<int, string> dic = new Dictionary<int, string>();
int index = 0;
for (int i = 0; i < data.Length; i++)
{
if (char.IsNumber(data[i]))
{
isDigit = true;
if (isChar)
{
dic.Add(index, sb.ToString() + "|" + sbWord.ToString());
index++;
isChar = false;
sb.Remove(0, sb.Length);
sbWord.Remove(0, sbWord.Length);
}
}
else
{
isDigit = false;
isChar = true;
sbWord.Append(data[i]);
}
if (isDigit)
sb.Append(data[i]);
if (i == data.Length - 1)
{
dic.Add(index, sb.ToString() + "|" + sbWord.ToString());
}
}
List<string> Position = new List<string>();
List<string> Article = new List<string>();
List<string> Quantity = new List<string>();
if (dic.Count > 0)
{
for (int i = 0; i < dic.Count; i++)
{
if (dic[i].Split('|')[1] == "Position")
Position.Add(dic[i].Split('|')[0]);
else if (dic[i].Split('|')[1] == "Article")
Article.Add(dic[i].Split('|')[0]);
else
Quantity.Add(dic[i].Split('|')[0]);
}
}
string[] Position_array = Position.ToArray();
string[] Article_array = Article.ToArray();
string[] Quantity_array = Quantity.ToArray();

Try this simple solution.
class StrSplit{
public static void main(String args[]){
int i;
String str = "1Position1234Article4321Quantity2Position4323Article3323Quantity";
String pattern= "(?<=Position)|(?<=Article)|(?<=Quantity)";
String[] parts = str.split(pattern);
List<String> Position = new ArrayList<String>();
List<String> Article = new ArrayList<String>();
List<String> Quantity = new ArrayList<String>();
for( i=0;i<parts.length;i++)
{
pattern="Position";
String[] subParts;
if(parts[i].contains(pattern))
{
subParts = parts[i].split(pattern);
Position.add(subParts[0]);
}
pattern="Article";
if(parts[i].contains(pattern))
{
subParts = parts[i].split(pattern);
Article.add(subParts[0]);
}
pattern="Quantity";
if(parts[i].contains(pattern))
{
subParts = parts[i].split(pattern);
Quantity.add(subParts[0]);
}
}
System.out.println("Position:");
for(i = 0; i < Position.size(); i++) {
System.out.println(Position.get(i));
}
System.out.println("Article:");
for(i = 0; i < Article.size(); i++) {
System.out.println(Article.get(i));
}
System.out.println("Quantity:");
for(i = 0; i < Quantity.size(); i++) {
System.out.println(Quantity.get(i));
}
}
}
Output:
Position:
1
2
Article:
1234
4323
Quantity:
4321
3323

Cutting a string into array of <"x" chars each [closed]

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This question does not appear to be about programming within the scope defined in the help center.
Closed 8 years ago.
Improve this question
I have a situation where my string can't go past a certain point, so what I want to do is cut it into smaller strings of "x" characters, and then print them one by one on top of each other. They don't all need to be equal, if x is 5, and I have an 11 character string, printing 3 lines with 5, 5, and 1 characters is fine. Is there an easy way to do this in C#?
Example:
string Test = "This is a test string";
stringarray = Cutup(Test, 5);
//Result:
//"This "
//"is a "
//"test "
//"strin"
//"g"

try something like this:
public string[] Cutcup(string s, int l)
{
List<string> result = new List<string>();
for (int i = 0; i < s.Length; i += l)
{
result.Add(s.Substring(i, Math.Min(5, s.Substring(i).Length)));
}
return result.ToArray();
}

You could cut up the strings then do a test.lastIndexOf(' '); If that helps

You can use the String Manipultion function Substring() and a for loop to accomplish this.

here is an example
int maxChars = 5;
String myStr = "This is some text used in testing this method of splitting a string and just a few more chars and the string is complete";
List<String> mySubStrings = new List<String>();
while (myStr.Length > maxChars)
{
mySubStrings.Add(myStr.Substring(0,maxChars));
myStr = myStr.Substring(maxChars);
}
mySubStrings.ToArray();

List<string> result = new List<string>();
string testString = "This is a test string";
string chunkBuilder = "";
int chunkSize = 5;
for (int i = 0; i <= testString.Length-1; i++)
{
chunkBuilder += testString[i];
if (chunkBuilder.Length == chunkSize || i == testString.Length - 1)
{
result.Add(chunkBuilder);
chunkBuilder = "";
}
}

Another try, with less string concatenations
string Test = "This is a test string";
List<string> parts = new List<string>();
int i = 0;
do
{
parts.Add(Test.Substring(i,System.Math.Min(5, Test.Substring(i).Length)));
i+= 5;
} while (i < Test.Length);

Here are a couple more ways. Cutup2 below is more efficient but less pretty. Both pass the test case given.
private static IEnumerable<string> Cutup(string given, int chunkSize)
{
var skip = 0;
var iterations = 0;
while (iterations * chunkSize < given.Length)
{
iterations++;
yield return new string(given.Skip(skip).Take(chunkSize).ToArray());
skip += chunkSize;
}
}
private static unsafe IEnumerable<string> Cutup2(string given, int chunkSize)
{
var pieces = new List<string>();
var consumed = 0;
while (consumed < given.Length)
{
fixed (char* g = given)
{
var toTake = consumed + chunkSize > given.Length
? given.Length - consumed
: chunkSize;
pieces.Add(new string(g, consumed, toTake));
}
consumed += chunkSize;
}
return pieces;
}

All in one line
var size = 5;
var results = Enumerable.Range(0, (int)Math.Ceiling(test.Length / (double)size))
.Select(i => test.Substring(i * size, Math.Min(size, test.Length - i * size)));

I once made an extensionmethod that can be used for this:
public static IEnumerable<IEnumerable<T>> Subsequencise<T>(this IEnumerable<T> input, int subsequenceLength)
{
var enumerator = input.GetEnumerator();
SubsequenciseParameter parameter = new SubsequenciseParameter { Next = enumerator.MoveNext() };
while (parameter.Next)
yield return getSubSequence(enumerator, subsequenceLength, parameter);
}
private static IEnumerable<T> getSubSequence<T>(IEnumerator<T> enumerator, int subsequenceLength, SubsequenciseParameter parameter)
{
do
{
yield return enumerator.Current;
} while ((parameter.Next = enumerator.MoveNext()) && --subsequenceLength > 0);
}
// Needed to let the Subsequencisemethod know when to stop, since you cant use out or ref parameters in an yield-return method.
class SubsequenciseParameter
{
public bool Next { get; set; }
}
then you can do this:
string Test = "This is a test string";
stringarray = Test.Subsequencise(5).Select(subsequence => new String(subsequence.Toarray())).Toarray();

Here's a rather LINQy one-liner:
static IEnumerable<string> SliceAndDice1( string s , int n )
{
if ( s == null ) throw new ArgumentNullException("s");
if ( n < 1 ) throw new ArgumentOutOfRangeException("n");
int i = 0 ;
return s.GroupBy( c => i++ / n ).Select( g => g.Aggregate(new StringBuilder() , (sb,c)=>sb.Append(c)).ToString() ) ;
}
If that gives you a headache, try the more straightforward
static IEnumerable<string> SliceAndDice2( string s , int n )
{
if ( s == null ) throw new ArgumentNullException("s") ;
if ( n < 1 ) throw new ArgumentOutOfRangeException("n") ;
int i = 0 ;
for ( i = 0 ; i < s.Length-n ; i+=n )
{
yield return s.Substring(i,n) ;
}
yield return s.Substring(i) ;
}

How to convert a list with splitted strings to a possible value sets?

I need to implement a module which will convert a List which with splitted string values to a possible value sets.
For Example
consider the list contains following values
1
1,2
3
4
5
The module should convert the above list to list of possible value sets
1,2,3,4,5
1,1,3,4,5
thanks in advance

This will do it, although it will return your example in the opposite order:
static IEnumerable<string> Permutations(
IEnumerable<string> input,
char separator)
{
var sepAsString = separator.ToString();
var enumerators = input
.Select(s => s.Split(separator).GetEnumerator())
.ToArray();
if (!enumerators.All(e => e.MoveNext())) yield break;
while (true)
{
yield return String.Join(sepAsString, enumerators.Select(e => e.Current));
if (enumerators.Reverse().All(e => {
bool finished = !e.MoveNext();
if (finished)
{
e.Reset();
e.MoveNext();
}
return finished;
}))
yield break;
}
}
Usage:
var list = new[] { "1", "1,2", "3", "4", "5" }.ToList();
var perms = Permutations(list, ',').ToList();

Rawling's answer is pretty solid, but i don't find it easy to read and understand. Here's another way, using less Linq.
private List<string> Process(IEnumerable<string> input)
{
List<string> data = new List<string>();
int preExpandCount = 0, offset = 0;
foreach (string inputItem in input)
{
List<string> splitItems = inputItem.Split(',').ToList();
if (data.Count > 0)
preExpandCount = ExpandList(data, splitItems.Count - 1);
offset = 0;
foreach (string splitItem in splitItems)
{
if (preExpandCount == 0)
data.Add(splitItem);
else
{
for (int i = 0; i < preExpandCount; i++)
data[i + offset] = String.Format("{0},{1}", data[i + offset], splitItem);
offset += preExpandCount;
}
}
}
return data.OrderBy(e => e).ToList();
}
private int ExpandList(List<string> existing, int count)
{
int existingCount = existing.Count;
for (int i = 0; i < count; i++)
existing.AddRange(existing.Take(existingCount).ToList());
return existingCount;
}

Develop Reference

C# (C-Sharp) is a programming language developed by Microsoft that runs on the .NET Framework.

Substract shortest string containing all search criteria - c#

Related

Sort order of files [duplicate]

Perform Linq Orderby generic list contain integer and string value [duplicate]

Searching for a string in a string

Cutting a string into array of <"x" chars each [closed]

How to convert a list with splitted strings to a possible value sets?

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