I have an ArrayList that contains a large number of strings. It needs to be sorted in place based on three fields (essentially three substrings) which are Name, Age and Amt. Age is the first substring (position 0-3), Name is second (3-6) and Amt is last (6-10). The order in which these parameters are to be sorted is very important and is as follows:
First perform ascending sort by Name THEN do ascending sort by Age (which actually comes earlier in the substring) and THEN do descending sort by Amt. That's it.
I have this class
public class ArrComparer : IComparer
{
public int Compare(object x, object y)
{
string left = x.ToString();
string right = y.ToString();
string lhs = left.Substring(3, 6);
string rhs = right.Substring(3, 6);
return lhs.CompareTo(rhs);
}
}
which I use to sort based on just one field - Name by invoking
RecordList.Sort(new ArrComparer());
This lets me sort correctly based on that one field. The question is how can I modify this code to allow me to sort based on all three AT ONCE, in the right order and using proper asc/desc mode?
Any code or tips would be greatly appreciated. (By the way, in case you are wondering using generic List<T> is not an option in this project).
ArrayList still implements IEnumerable, meaning you can use the simple orderby() and thenby() extensions in linq:
RecordList = new ArrayList(
RecordList.Cast<string>().OrderBy(s => s.Substring(3,3))
.ThenBy(s => int.Parse(s.Substring(0,3)))
.ThenByDescending(s => double.Parse(s.Substring(6,4)))
.ToArray());
Other ways to express this include building a more complicated .OrderBy() or using an anonymous type to compose your string as an object:
RecordList = new ArrayList(
Record.Cast<string>().Select(s => new {source = s, age = int.Parse(s.Substring(0, 3)), name = s.Substring(3,3), amt = double.Parse(s.Substring(6,4))})
.OrderBy(o => o.name)
.ThenBy(o => o.age)
.ThenByDescending(o => o.amt)
.Select(o => o.source).ToArray());
I like that option because it sets you up to start thinking in terms objects. Play your cards right and you can skip that last .Select() projection to keep the objects rather than going back to strings, which will save the work of having to do all that parsing over again later.
If these aren't an option (possibly for the same reason you can't use List<T>), it's easy to modify your existing compare method like so:
public class ArrComparer : IComparer
{
public int Compare(object x, object y)
{
int result;
string left = x.ToString();
string right = y.ToString();
string lhs1 = left.Substring(3, 3);
string rhs1 = right.Substring(3, 3);
result = lhs1.CompareTo(rhs1);
if (result == 0)
{
int lhs2 = int.Parse(left.Substring(0,3));
int rhs2 = int.Parse(right.Substring(0,3));
result = lhs2.CompareTo(rhs2);
}
if (result == 0)
{
double lhs3 = double.Parse(left.Substring(6,4));
double rhs3 = double.Parse(right.Substring(6,4));
result = rhs3.CompareTo(lhs3);
}
return result;
}
}
You can compare part by part:
string left = (string)x;
string right = (string)y;
string lname = left.Substring(3, 3);
string rname = right.Substring(3, 3);
int result = lname.CompareTo(rname);
if (result != 0) return result;
string lage = left.Substring(0, 3);
string rage = right.Substring(0, 3);
int result = lage.CompareTo(rage);
if (result != 0) return result;
string lamt = left.Substring(6);
string ramt = right.Substring(6);
return -lamt.CompareTo(ramt);
If you need an IComparer, try something like:
public class ArrComparer : IComparer
{
public int Compare(object x, object y)
{
string left = x.ToString();
string right = y.ToString();
string leftName = left.Substring([whatever]);
string rightName = right.Substring([whatever]);
// First try comparing names
int result = leftName.CompareTo(rightName);
if (result != 0)
{
return result;
}
// If that didn't work, compare ages
string leftAge = left.Substring([whatever]);
string rightAge = right.Substring([whatever]);
result = leftAge.CompareTo(rightAge);
if (result != 0)
{
return result;
}
// Finally compare amounts (descending)
string leftAmt = left.Substring([whatever]);
string rightAmt = right.Substring([whatever]);
result = -leftAmt.CompareTo(rightAmt); // Minus for descending
return result;
}
}
I would recommend storing your records in an object, and make those comparable instead.
In order to compare all three fields using the same method you are currently using you simply need to extract all three pieces of data and do a full comparison.
public class ArrComparer : IComparer
{
public int Compare(object x, object y)
{
string left = x.ToString();
string right = y.ToString();
// Note I assumed indexes since yours were overlapping.
string lage = left.Substring(0, 3);
string lname = left.Substring(3, 3);
string lamt = left.Substring(7, 3);
string rage = left.Substring(0, 3);
string rname = left.Substring(3, 3);
string ramt = left.Substring(7, 3);
// Compare name first, if one is greater return
int result = lname.CompareTo(rname);
if (result != 0)
return result;
// else compare age, if one is greater return
result = lage.CompareTo(rage)
if (result != 0)
return result;
// else compare amt if one is greater return
result = lamt.CompareTo(ramt)
if (result != 0)
return result;
// else they are equal
return 0;
}
}
you could expend your ArrCompare with if statements like if(rhs == lhs) compere with other part of string.
Accen deccend is meeter of return -1 or 1
Related
Similar to this question, I'm trying to iterate only distinct values of sub-string of given strings, for example:
List<string> keys = new List<string>()
{
"foo_boo_1",
"foo_boo_2,
"foo_boo_3,
"boo_boo_1"
}
The output for the selected distinct values should be (select arbitrary the first sub-string's distinct value):
foo_boo_1 (the first one)
boo_boo_1
I've tried to implement this solution using the IEqualityComparer with:
public class MyEqualityComparer : IEqualityComparer<string>
{
public bool Equals(string x, string y)
{
int xIndex = x.LastIndexOf("_");
int yIndex = y.LastIndexOf("_");
if (xIndex > 0 && yIndex > 0)
return x.Substring(0, xIndex) == y.Substring(0, yIndex);
else
return false;
}
public int GetHashCode(string obj)
{
return obj.GetHashCode();
}
}
foreach (var key in myList.Distinct(new MyEqualityComparer()))
{
Console.WriteLine(key)
}
But the resulted output is:
foo_boo_1
foo_boo_2
foo_boo_3
boo_boo_1
Using the IEqualityComparer How do I remove the sub-string distinct values (foo_boo_2 and foo_boo_3)?
*Please note that the "real" keys are a lot longer, something like "1_0_8-B153_GF_6_2", therefore I must use the LastIndexOf.
Your current implementation has some flaws:
Both Equals and GetHashCode must never throw exception (you have to check for null)
If Equals returns true for x and y then GetHashCode(x) == GetHashCode(y). Counter example is "abc_1" and "abc_2".
The 2nd error can well cause Distinct return incorrect results (Distinct first compute hash).
Correct code can be something like this
public class MyEqualityComparer : IEqualityComparer<string> {
public bool Equals(string x, string y) {
if (ReferenceEquals(x, y))
return true;
else if ((null == x) || (null == y))
return false;
int xIndex = x.LastIndexOf('_');
int yIndex = y.LastIndexOf('_');
if (xIndex >= 0)
return (yIndex >= 0)
? x.Substring(0, xIndex) == y.Substring(0, yIndex)
: false;
else if (yIndex >= 0)
return false;
else
return x == y;
}
public int GetHashCode(string obj) {
if (null == obj)
return 0;
int index = obj.LastIndexOf('_');
return index < 0
? obj.GetHashCode()
: obj.Substring(0, index).GetHashCode();
}
}
Now you are ready to use it with Distinct:
foreach (var key in myList.Distinct(new MyEqualityComparer())) {
Console.WriteLine(key)
}
Your GetHashCode method in your equality comparer is returning the hash code for the entire string, just make it hash the substring, for example:
public int GetHashCode(string obj)
{
var index = obj.LastIndexOf("_");
return obj.Substring(0, index).GetHashCode();
}
For a more succinct solution that avoids using a custom IEqualityComparer<>, you could utilise GroupBy. For example:
var keys = new List<string>()
{
"foo_boo_1",
"foo_boo_2",
"foo_boo_3",
"boo_boo_1"
};
var distinct = keys
.Select(k => new
{
original = k,
truncated = k.Contains("_") ? k.Substring(0, k.LastIndexOf("_")) : k
})
.GroupBy(k => k.truncated)
.Select(g => g.First().original);
This outputs:
foo_boo_1
boo_boo_1
I currently have a list of coordinates that I need sorted. Each line represents Longitude, Latitude. I need to sort only on the Longitude.
It is stored in an string array:
string[] coords = fpdp.Coordinates.ToArray();
Here is the original list:
**LongLat**
98.63,85.02
43.08,79.07
26.97,70.88
18.8,62.3
13.47,53.5
8.57,44.8
3.58,36.35
-1.63,28.2
-6.93,20.33
-12.12,12.63
-17.17,5.02
-22.63,-2.25
-28.22,-9.43
-34.98,-15.7
-42.67,-21.08
-51.18,-25.62
-60.55,-29.12
-70.7,-31.12
-81.2,-31.18
-91.42,-29.72
-101.02,-26.97
-109.62,-22.85
-117.3,-17.83
-123.9,-11.9
-129.32,-5.05
-133.55,2.47
-136.9,10.3
-140.45,17.78
-144.75,24.98
-148.6,32.53
-152.02,40.37
-155.85,48.28
-160.8,56.27
-165.75,64.48
-172.62,72.78
171.35,80.83
98.93,85.17
Here is what I need it to look like. It is sorted by Large to small for positive numbers, and small to large for negative numbers. Only focusing on the first longitude coordinate:
**LongLat-Sorted**
171.35,80.83
98.93,85.17
98.63,85.02
43.08,79.07
26.97,70.88
18.8,62.3
13.47,53.5
8.57,44.8
3.58,36.35
-1.63,28.2
-6.93,20.33
-12.12,12.63
-17.17,5.02
-22.63,-2.25
-28.22,-9.43
-34.98,-15.7
-42.67,-21.08
-51.18,-25.62
-60.55,-29.12
-70.7,-31.12
-81.2,-31.18
-91.42,-29.72
-101.02,-26.97
-109.62,-22.85
-117.3,-17.83
-123.9,-11.9
-129.32,-5.05
-133.55,2.47
-136.9,10.3
-140.45,17.78
-144.75,24.98
-148.6,32.53
-152.02,40.37
-155.85,48.28
-160.8,56.27
-165.75,64.48
-172.62,72.78
How can I accomplish this in code? Any help would be great.
SOLUTION:
I tweaked this to the following, and it's working. Thanks a lot! :)
public class LongLatSort : IComparer
{
int IComparer.Compare(Object x, Object y)
{
string[] longLatParts1 = Convert.ToString(x).Split(',');
string[] longLatParts2 = Convert.ToString(y).Split(',');
var var1 = double.Parse(longLatParts1[0]);
var var2 = double.Parse(longLatParts2[0]);
if (var1 > var2)
{
return -1; // flipped for descending
}
else if (var1 < var2)
{
return 1; // flipped for descending
}
// secondary sort on latitude when values are equal
return var1 > var2 ? -1 : 1; // flipped for descending
}
}
Just finished tested this, seems to work.
class SimplePoint
{
public SimplePoint(string coord)
{
var coords = coord.Split(',').Select(s => double.Parse(s, System.Globalization.CultureInfo.InvariantCulture)).ToArray();
X = coords[0];
Y = coords[1];
}
public double X;
public double Y;
public override string ToString()
{
return X.ToString() + "," + Y.ToString();
}
}
static class LongLatParseAndSort
{
public static string SortedLongLat(string unsorted)
{
return unsorted
.Split(' ')
.Select(c => new SimplePoint(c))
.OrderByDescending(sp => sp.X)
.Select(sp => sp.ToString())
.Aggregate((a, b) => a += b);
}
}
How is this data stored? An array of Strings? or a 2-dimensional array or floats? or an Array of some structure with a lat and long? I'll assume its an array of LongLat since thats how you worded it.
EDIT I realized your subject title said string, so I added a constructor to convert from string to a LongLat.
Your desired result looks sorted descending on Longitude.
This code is untested, forgive me if it's not 100% but you get the idea.
// This is pretending to be the data structure you are using
public class LongLat {
private float mLongitude;
private float mLatitude;
// constructor from string for convenience
public LongLat(string longLatString ) {
string[] longLatParts = longLatString.Split(',');
mLongitude = float.Parse(longLatParts[0]);
mLatitude = float.Parse(longLatParts[1]);
}
public float Longitude {get; set; }
public float Latitude {get; set; }
}
// The sorter
public class LongLatSort : IComparer {
public int IComparer.Compare(object a, object b) {
LongLat o1=(LongLat)a;
LongLat o2=(LongLat)b;
if (o1.Longitude > o2.Longitude) {
return -1; // flipped for descending
} else if ( o1.Latitude < o2.Longitude ) {
return 1; // flipped for descending
}
// secondary sort on latitude when values are equal
return o1.Latitude > o2.Latitude ? -1 : 1; // flipped for descending
}
}
// now you should be able to use the sorter something like this?
// though best to not instantiate the Comparer every time but you get the idea
// EDIT: create your array of LongLats from strings first
Arrays.Sort( yourArrayofLongLats, new LongLastSort() );
I have a large list and I would like to overwrite one value if required. To do this, I create two subsets of the list which seems to give me an OutOfMemoryException. Here is my code snippet:
if (ownRG != "")
{
List<string> maclist = ownRG.Split(',').ToList();
List<IVFile> temp = powlist.Where(a => maclist.Contains(a.Machine)).ToList();
powlist = powlist.Where(a => !maclist.Contains(a.Machine)).ToList(); // OOME Here
temp.ForEach(a => { a.ReportingGroup = ownRG; });
powlist.AddRange(temp);
}
Essentially I'm splitting the list into the part that needs updating and the part that doesn't, then I perform the update and put the list back together. This works fine for smaller lists, but breaks with an OutOfMemoryException on the third row within the if for a large list. Can I make this more efficient?
NOTE
powlist is the large list (>1m) items. maclist only has between 1 and 10 but even with 1 item this breaks.
Solving your issue
Here is how to rearrange your code using the enumerator code from my answer:
if (!string.IsNullOrEmpty(ownRG))
{
var maclist = new CommaSeparatedStringEnumerable(str);
var temp = powlist.Where(a => maclist.Contains(a.Machine));
foreach (var p in temp)
{
p.ReportingGroup = ownRG;
}
}
You should not use ToList in your code.
You don't need to remove thee contents of temp from powlist (you are re-adding them anyway)
Streaming over a large comma-separated string
You can iterate over the list manually instead of doing what you do now, by looking for , characters and remembering the position of the last found one and the one before. This will definitely make your app work because then it won't need to store the entire set in the memory at once.
Code example:
var str = "aaa,bbb,ccc";
var previousComma = -1;
var currentComma = 0;
for (; (currentComma = str.IndexOf(',', previousComma + 1)) != -1; previousComma = currentComma)
{
var currentItem = str.Substring(previousComma + 1, currentComma - previousComma - 1);
Console.WriteLine(currentItem);
}
var lastItem = str.Substring(previousComma + 1);
Console.WriteLine(lastItem);
Custom iterator
If you want to do it 'properly' in a fancy way, you can even write a custom enumerator:
public class CommaSeparatedStringEnumerator : IEnumerator<string>
{
int previousComma = -1;
int currentComma = -1;
string bigString = null;
bool atEnd = false;
public CommaSeparatedStringEnumerator(string s)
{
if (s == null)
throw new ArgumentNullException("s");
bigString = s;
this.Reset();
}
public string Current { get; private set; }
public void Dispose() { /* No need to do anything here */ }
object IEnumerator.Current { get { return this.Current; } }
public bool MoveNext()
{
if (atEnd)
return false;
atEnd = (currentComma = bigString.IndexOf(',', previousComma + 1)) == -1;
if (!atEnd)
Current = bigString.Substring(previousComma + 1, currentComma - previousComma - 1);
else
Current = bigString.Substring(previousComma + 1);
previousComma = currentComma;
return true;
}
public void Reset()
{
previousComma = -1;
currentComma = -1;
atEnd = false;
this.Current = null;
}
}
public class CommaSeparatedStringEnumerable : IEnumerable<string>
{
string bigString = null;
public CommaSeparatedStringEnumerable(string s)
{
if (s == null)
throw new ArgumentNullException("s");
bigString = s;
}
public IEnumerator<string> GetEnumerator()
{
return new CommaSeparatedStringEnumerator(bigString);
}
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
}
Then you can iterate over it like this:
var str = "aaa,bbb,ccc";
var enumerable = new CommaSeparatedStringEnumerable(str);
foreach (var item in enumerable)
{
Console.WriteLine(item);
}
Other thoughts
Can I make this more efficient?
Yes, you can. I suggest to either work with a more efficient data format (you can take a look around databases or XML, JSON, etc. depending on your needs). If you really want to work with comma-separated items, see my code examples above.
There's no need to create a bunch of sub-lists from powlist and reconstruct it. Simply loop over the powlist and update the ReportingGroup property accordingly.
var maclist = new HashSet<string>( ownRG.Split(',') );
foreach( var item in powlist) {
if( maclist.Contains( item.Machine ) ){
item.ReportingGroup = ownRG;
}
}
Since this changes powlist in place, you won't allocate any extra memory and shouldn't run into an OutOfMemoryException.
In a loop find the next ',' char. Take the substring between the ',' and the previous ',' position. At the end of the loop save a reference to the previous ',' position (which is initially set to 0). So you parse the items one-by-one rather than all at once.
You can try looping the items of your lists, but this will increase processing time.
foreach(var item in powlist)
{
//do your opeartions
}
I am trying to implement the IComparable interface in my custom object so that List.Sort() can sort them alphabetically.
My object has a field called _name which is a string type, and I want it to sort based on that. Here is the method I implemented:
public int CompareTo(object obj)
{
//Int reference table:
//1 or greater means the current instance occurs after obj
//0 means both elements occur in the same position
//-1 or less means the current instance occurs before obj
if (obj == null)
return 1;
Upgrade otherUpgrade = obj as Upgrade;
if (otherUpgrade != null)
return _name.CompareTo(otherUpgrade.Name);
else
throw new ArgumentException("Passed object is not an Upgrade.");
}
Not sure if I did something wrong or if it's just the way the string CompareTo works, but basically my List was sorted like this:
Test Upgrade
Test Upgrade 10
Test Upgrade 11
Test Upgrade 12
Test Upgrade 13
Test Upgrade 14
Test Upgrade 15
Test Upgrade 2
Test Upgrade 3
Test Upgrade 4
Test Upgrade 5
I want them to be sorted like this:
Test Upgrade
Test Upgrade 2
Test Upgrade 3
...etc
You want "natural order" -- the collation that a human who is familiar with the conventions of English would choose -- as opposed to what you've got, which is "lexicographic" collation: assign every letter a strict ordering, and then sort by each letter in turn.
Jeff has a good article on some of the ins and outs here, with links to different algorithms that try to solve the problem:
http://www.codinghorror.com/blog/2007/12/sorting-for-humans-natural-sort-order.html
and Raymond discussed how Windows dealt with it here:
http://technet.microsoft.com/en-us/magazine/hh475812.aspx
Basically the problem is: natural order collation requires solving an artificial intelligence problem; you're trying to emulate what a human would do, and that can be surprisingly tricky. Good luck!
Strings are sorted in lexicographic order. You'll have to either format all your numbers to have the same length (eg: Test Upgrade 02) or parse the number in your comparer and incorporate it in your comparison logic.
The reason this happens is that you are doing string comparison, which has no explicit knowledge of numbers. It orders each string by the respective character codes of each character.
To get the effect you want will require a bit more work. See this question: Sort on a string that may contain a number
AlphaNumeric Sorting
public class AlphanumComparatorFast : IComparer
{
public int Compare(object x, object y)
{
string s1 = x as string;
if (s1 == null)
{
return 0;
}
string s2 = y as string;
if (s2 == null)
{
return 0;
}
int len1 = s1.Length;
int len2 = s2.Length;
int marker1 = 0;
int marker2 = 0;
// Walk through two the strings with two markers.
while (marker1 < len1 && marker2 < len2)
{
char ch1 = s1[marker1];
char ch2 = s2[marker2];
// Some buffers we can build up characters in for each chunk.
char[] space1 = new char[len1];
int loc1 = 0;
char[] space2 = new char[len2];
int loc2 = 0;
// Walk through all following characters that are digits or
// characters in BOTH strings starting at the appropriate marker.
// Collect char arrays.
do
{
space1[loc1++] = ch1;
marker1++;
if (marker1 < len1)
{
ch1 = s1[marker1];
}
else
{
break;
}
} while (char.IsDigit(ch1) == char.IsDigit(space1[0]));
do
{
space2[loc2++] = ch2;
marker2++;
if (marker2 < len2)
{
ch2 = s2[marker2];
}
else
{
break;
}
} while (char.IsDigit(ch2) == char.IsDigit(space2[0]));
// If we have collected numbers, compare them numerically.
// Otherwise, if we have strings, compare them alphabetically.
string str1 = new string(space1);
string str2 = new string(space2);
int result;
if (char.IsDigit(space1[0]) && char.IsDigit(space2[0]))
{
int thisNumericChunk = int.Parse(str1);
int thatNumericChunk = int.Parse(str2);
result = thisNumericChunk.CompareTo(thatNumericChunk);
}
else
{
result = str1.CompareTo(str2);
}
if (result != 0)
{
return result;
}
}
return len1 - len2;
}
}
Usage :
using System;
using System.Collections;
class Program
{
static void Main()
{
string[] highways = new string[]
{
"100F",
"50F",
"SR100",
"SR9"
};
//
// We want to sort a string array called highways in an
// alphanumeric way. Call the static Array.Sort method.
//
Array.Sort(highways, new AlphanumComparatorFast());
//
// Display the results
//
foreach (string h in highways)
{
Console.WriteLine(h);
}
}
}
Output
50F 100F SR9 SR100
Thanks for all the replies guys. I did my own method and it seems to work fine. It doesn't work for all cases but it works for my scenario. Here is the code for anyone who is interested:
/// <summary>
/// Compares the upgrade to another upgrade
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public int CompareTo(object obj)
{
//Int reference table:
//1 or greater means the current instance occurs after obj
//0 means both elements occur in the same position
//-1 or less means the current instance occurs before obj
if (obj == null)
return 1;
Upgrade otherUpgrade = obj as Upgrade;
if (otherUpgrade != null)
{
//Split strings into arrays
string[] splitStringOne = _name.Split(new char[] { ' ' });
string[] splitStringTwo = otherUpgrade.Name.Split(new char[] { ' ' });
//Will hold checks to see which comparer will be used
bool sameWords = false, sameLength = false, bothInt = false;
//Will hold the last part of the string if it is an int
int intOne = 0, intTwo = 0;
//Check if they have the same length
sameLength = (splitStringOne.Length == splitStringTwo.Length);
if (sameLength)
{
//Check to see if they both end in an int
bothInt = (int.TryParse(splitStringOne[splitStringOne.Length - 1], out intOne) && int.TryParse(splitStringTwo[splitStringTwo.Length - 1], out intTwo));
if (bothInt)
{
//Check to see if the previous parts of the string are equal
for (int i = 0; i < splitStringOne.Length - 2; i++)
{
sameWords = (splitStringOne[i].ToLower().Equals(splitStringTwo[i].ToLower()));
if (!sameWords)
break;
}
}
}
//If all criteria is met, use the customk comparer
if (sameWords && sameLength && bothInt)
{
if (intOne < intTwo)
return -1;
else if (intOne > intTwo)
return 1;
else //Both equal
return 0;
}
//Else use the default string comparer
else
return _name.CompareTo(otherUpgrade.Name);
}
else
throw new ArgumentException("Passed object is not an Upgrade.");
}
Will work for strings spaced out using a " " character, like so:
Test data:
Hello 11
Hello 2
Hello 13
Result
Hello 2
Hello 11
Hello 13
Will not work for data such as Hello11 and Hello2 since it cannot split them. Not case sensitive.
I have an unordered list that can look something like this:
1
2.2
1.1.1
3
When i sort the list, 1.1.1 becomes greater than 3 and 2.2, and 2.2 becomes greater than 3.
This is because Double.Parse removes the dots and makes it a whole number.
This is the method i use to sort with:
public class CompareCategory: IComparer<Category>
{
public int Compare(Category c1, Category c2)
{
Double cat1 = Double.Parse(c1.prefix);
Double cat2 = Double.Parse(c2.prefix);
if (cat1 > cat2)
return 1;
else if (cat1 < cat2)
return -1;
else
return 0;
}
}
How can i fix this?
Thanks
Are these version #s by chance? Can you use the Version class? It sorts each part as you seem to want, although it only works up to 4 parts. I would not recommend parsing into a numeric value like you are doing.
It has an IComparable interface. Assuming your inputs are strings, here's a sample:
public class CompareCategory: IComparer<Category>
{
public int Compare(Category c1, Category c2)
{
var cat1 = new Version(c1.prefix);
var cat2 = new Version(c2.prefix);
if (cat1 > cat2)
return 1;
else if (cat1 < cat2)
return -1;
else
return 0;
}
}
If you need something with more than 4 "parts", I think I would create a comparer which split the strings at the dots, and then parse each element as an integer and compare them numerically. Make sure to consider cases like 1.002.3 and 1.3.3 (what do you want the sort order to be?).
Update, here is a sample of what I mean. Lightly tested:
public class CategoryComparer : Comparer<Category>
{
public override int Compare(Category x, Category y)
{
var xParts = x.prefix.Split(new[] { '.' });
var yParts = y.prefix.Split(new[] { '.' });
int index = 0;
while (true)
{
bool xHasValue = xParts.Length > index;
bool yHasValue = yParts.Length > index;
if (xHasValue && !yHasValue)
return 1; // x bigger
if (!xHasValue && yHasValue)
return -1; // y bigger
if (!xHasValue && !yHasValue)
return 0; // no more values -- same
var xValue = decimal.Parse("." + xParts[index]);
var yValue = decimal.Parse("." + yParts[index]);
if (xValue > yValue)
return 1; // x bigger
if (xValue < yValue)
return -1; // y bigger
index++;
}
}
}
public static void Main()
{
var categories = new List<Category>()
{
new Category { prefix = "1" },
new Category { prefix = "2.2" },
new Category { prefix = "1.1.1" },
new Category { prefix = "1.1.1" },
new Category { prefix = "1.001.1" },
new Category { prefix = "3" },
};
categories.Sort(new CategoryComparer());
foreach (var category in categories)
Console.WriteLine(category.prefix);
}
Output:
1
1.001.1
1.1.1
1.1.1
2.2
3
public class CodeComparer : IComparer<string>
{
public int Compare(string x, string y)
{
var xParts = x.Split(new char[] { '.' });
var yParts = y.Split(new char[] { '.' });
var partsLength = Math.Max(xParts.Length, yParts.Length);
if (partsLength > 0)
{
for (var i = 0; i < partsLength; i++)
{
if (xParts.Length <= i) return -1;// 4.2 < 4.2.x
if (yParts.Length <= i) return 1;
var xPart = xParts[i];
var yPart = yParts[i];
if (string.IsNullOrEmpty(xPart)) xPart = "0";// 5..2->5.0.2
if (string.IsNullOrEmpty(yPart)) yPart = "0";
if (!int.TryParse(xPart, out var xInt) || !int.TryParse(yPart, out var yInt))
{
// 3.a.45 compare part as string
var abcCompare = xPart.CompareTo(yPart);
if (abcCompare != 0)
return abcCompare;
continue;
}
if (xInt != yInt) return xInt < yInt ? -1 : 1;
}
return 0;
}
// compare as string
return x.CompareTo(y);
}
}
Maybe you could just string compare it?
I'm surprised that Double.Parse doesn't throw an exception with those numbers with more than one decimal place.
You really need to write some rules about how to compare these strings.
I would split the strings using String.Split() on the dot character, then iterate through the two lists created and as soon as one of the levels contained a lower or higher number than the other, or if you ran out of items in one of the lists then you wold return 1 or -1 as appropriate. If you get to the end of both lists in the same iteration of the loop then they are the same and return 0.
I would write the code but I don't have VS in front of me.