I have to extract summary from newspaper article . The summary is extracted based on given Keyword and according to below mentioned rules .
Summary should be of 200 characters.
Start printing from that sentence in article as soon as keyword
appears in that sentence and print upto 200 characters
If the matching sentence occurs towards ending of article such that
summary is coming out to be less than 200 characters , then move
back from matching sentence towards previous sentences uptill
finally 200 charcters containing matching sentence are printed
finally.
What I have done untill now is ...
var regex = new Regex(keyword+#"(.{0,200})");
foreach (Match match in regex.Matches(input))
{
var result = match.Groups[1].Value;
Console.WriteLine(result);
// work with the result
}
The above code successfully reaches the first matching sentence but starts printing AFTER the keyword upto 200 characters rather than beginning of matching sentence.
Also there is no backtracking if end of article is reached before 200 characters are printed.
Please guide me how should I proceed . Even if somebody doesn't know complete solution , PLEASE do help me out in sub parts of question .
var nextIndex = input.IndexOf(keyword);
while (nextIndex != -1)
{
var index = nextIndex;
// To start the 200chars result from right after the keyword, do instead:
// var index = nextIndex + keyword.Length;
// If you want to stop after you reached the end of the text once:
// var end = false;
if (index + 200 >= input.Length)
{
index = input.Length - 200;
// If you want to stop after you reached the end of the text once:
// var end = true;
}
var result = index < 0 ? input : input.Substring(index, 200);
Console.WriteLine(result);
// If you want to stop after you reached the end of the text once:
// if (end) { break; }
nextIndex = input.IndexOf(keyword, nextIndex + 1);
}
And if you want to search to be case insensitive, just add StringComparison.OrdinalIgnoreCase as another parameter in both IndexOfs.
Use this instead,
var regex = new Regex( #"(" + keyword+ #".{0,200})");
This will make sure that the keyword is also included. Otherwise you can also use this
var result = match.Value;
Further you have specified {0,200} so it will match any instance which is of size between 0 and 200 so it will match any number of characters until the end of article is reached. Let me exactly know what you want to achieve in this regard.
If you want the expression to return the result from the start of the sentence, try doing this
var regex = new Regex( #"\.(.+?" + keyword+ #".*)");
But in this case, you will have to manually remove the excess characters as this regular expression tends to fetch more characters then you expected. It will fetch characters from the beginning of the sentence containing the keyword till the end of paragraph.
Is using regex a requirement? Here's a rough alternative if it's not:
var index = input.IndexOf(keyword) + keyword.Length;
var remaining = input.Length - index;
index = remaining >= 200 ? index : index -= 200 - remaining;
Console.WriteLine(input.Substring(index, 200));
Related
I know there are quite a few of these questions on SO, but I can't find one that explains how they implemented the pattern to return the N'th match, that was broken down. All the answers I looked just give the code to the OP with minimal explanation.
What I know is, you need to implement this {X} in the pattern where the X is the number occurrence you want to return.
So I am trying to match a string between two chars and I seemed to have been able to get that working.
The string to be tested looks something like this,
"=StringOne&=StringTwo&=StringThree&=StringFour&"
"[^/=]+(?=&)"
Again, after reading as much as I could, this pattern will also return all matches,
[^/=]+(?=&){1}
Due to {1} being the default and therefore redundant in the above pattern.
But I can't do this,
[^/=]+(?=&){2}
As it will not return 3rd match as I was expecting it too.
So could someone please shove me in the right direction and explain how to get the pattern needed to find the occurrence of the match that will be needed?
A pure regex way is possible, but is not really very efficient if your pattern is complex.
var s = "=StringOne&=StringTwo&=StringThree&=StringFour&";
var idx = 2; // Replace this occurrence
var result = Regex.Replace(s, $#"^(=(?:[^=&]+&=){{{idx-1}}})[^=&]+", "${1}REPLACED");
Console.WriteLine(result); // => =StringOne&=REPLACED&=StringThree&=StringFour&
See this C# demo and the regex demo.
Regex details
^ - start of string
(=(?:[^=&]+&=){1}) - Group 1 capturing:
= - a = symbol
(?:[^=&]+&=){1} - 1 occurrence (this number is generated dynamically) of
[^=&]+ - 1 or more chars other than = and & (NOTE that in case the string may contain = and &, it is safer to replace it with .*? and pass RegexOptions.Singleline option to the regex compiler)
&= - a &= substring.
[^=&]+ - 1 or more chars other than = and &
The ${1} in the replacement pattern inserts the contents of Group 1 back into the resulting string.
As an alternative, I can suggest introducing a counter and increment is upon each match, and only replace the one when the counter is equal to the match occurrence you specify.
Use
var s = "=StringOne&=StringTwo&=StringThree&=StringFour&";
var idx_to_replace = 2; // Replace this occurrence
var cnt = 0; // Counter
var result = Regex.Replace(s, "[^=]+(?=&)", m => { // Match evaluator
cnt++; return cnt == idx_to_replace ? "REPLACED" : m.Value; });
Console.WriteLine(result);
// => =StringOne&=REPLACED&=StringThree&=StringFour&
See the C# demo.
The cnt is incremented inside the match evaluator inside Regex.Replace and m is assigned the current Match object. When cnt is equal to idx_to_replace the replacement occurs, else, the whole match is pasted back (with m.Value).
Another approach is to iterate through the matches, and once the Nth match is found, replace it by splitting the string into parts before the match and after the match breaking out of the loop once the replacement is done:
var s = "=StringOne&=StringTwo&=StringThree&=StringFour&";
var idx_to_replace = 2; // Replace this occurrence
var cnt = 0; // Counter
var result = string.Empty; // Final result variable
var rx = "[^=]+(?=&)"; // Pattern
for (var m=Regex.Match(s, rx); m.Success; m = m.NextMatch())
{
cnt++;
if (cnt == idx_to_replace) {
result = $"{s.Substring(0, m.Index)}REPLACED{s.Substring(m.Index+m.Length)}";
break;
}
}
Console.WriteLine(result); // => =StringOne&=REPLACED&=StringThree&=StringFour&
See another C# demo.
This might be quicker since the engine does not have to find all matches.
I am seeking a way to search a string for an exact match or whole word match. RegEx.Match and RegEx.IsMatch don't seem to get me where I want to be. Consider the following scenario:
namespace test
{
class Program
{
static void Main(string[] args)
{
string str = "SUBTOTAL 34.37 TAX TOTAL 37.43";
int indx = str.IndexOf("TOTAL");
string amount = str.Substring(indx + "TOTAL".Length, 10);
string strAmount = Regex.Replace(amount, "[^.0-9]", "");
Console.WriteLine(strAmount);
Console.WriteLine("Press any key to continue...");
Console.ReadKey();
}
}
}
The output of the above code is:
// 34.37
// Press any key to continue...
The problem is, I don't want SUBTOTAL, but IndexOf finds the first occurrence of the word TOTAL which is in SUBTOTAL which then yields the incorrect value of 34.37.
So the question is, is there a way to force IndexOf to find only an exact match or is there another way to force that exact whole word match so that I can find the index of that exact match and then perform some useful function with it. RegEx.IsMatch and RegEx.Match are, as far as I can tell, simply boolean searches. In this case, it isn't enough to just know the exact match exists. I need to know where it exists in the string.
Any advice would be appreciated.
You can use Regex
string str = "SUBTOTAL 34.37 TAX TOTAL 37.43";
var indx = Regex.Match(str, #"\WTOTAL\W").Index; // will be 18
My method is faster than the accepted answer because it does not use Regex.
string str = "SUBTOTAL 34.37 TAX TOTAL 37.43";
var indx = str.IndexOfWholeWord("TOTAL");
public static int IndexOfWholeWord(this string str, string word)
{
for (int j = 0; j < str.Length &&
(j = str.IndexOf(word, j, StringComparison.Ordinal)) >= 0; j++)
if ((j == 0 || !char.IsLetterOrDigit(str, j - 1)) &&
(j + word.Length == str.Length || !char.IsLetterOrDigit(str, j + word.Length)))
return j;
return -1;
}
You can use word boundaries, \b, and the Match.Index property:
var text = "SUBTOTAL 34.37 TAX TOTAL 37.43";
var idx = Regex.Match(text, #"\bTOTAL\b").Index;
// => 19
See the C# demo.
The \bTOTAL\b matches TOTAL when it is not enclosed with any other letters, digits or underscores.
If you need to count a word as a whole word if it is enclosed with underscores, use
var idx = Regex.Match(text, #"(?<![^\W_])TOTAL(?![^\W_])").Index;
where (?<![^\W_]) is a negative lookbehind that fails the match if there is a character other than a non-word and underscore immediately to the left of the current location (so, there can be a start of string position, or a char that is a not a digit nor letter), and (?![^\W_]) is a similar negative lookahead that only matches if there is an end of string position or a char other than a letter or digit immediately to the right of the current location.
If the boundaries are whitespaces or start/end of string use
var idx = Regex.Match(text, #"(?<!\S)TOTAL(?!\S)").Index;
where (?<!\S) requires start of string or a whitespace immediately on the left, and (?!\S) requires the end of string or a whitespace on the right.
NOTE: \b, (?<!...) and (?!...) are non-consuming patterns, that is the regex index does not advance when matching these patterns, thus, you get the exact positions of the word you search for.
To make the accepted answer a little bit safer (since IndexOf returns -1 for unmatched):
string pattern = String.Format(#"\b{0}\b", findTxt);
Match mtc = Regex.Match(queryTxt, pattern);
if (mtc.Success)
{
return mtc.Index;
}
else
return -1;
While this may be a hack that just works for only your example, try
string amount = str.Substring(indx + " TOTAL".Length, 10);
giving an extra space before total. As this will not occur with SUBTOTAL, it should skip over the word you don't want and just look for an isolated TOTAL.
I'd recommend the Regex solution from L.B. too, but if you can't use Regex, then you could use String.LastIndexOf("TOTAL"). Assuming the TOTAL always comes after SUBTOTAL?
http://msdn.microsoft.com/en-us/library/system.string.lastindexof(v=vs.110).aspx
I have the following string:
This isMyTest testing
I want to get isMyTest as a result. I only have two first characters available("is"). The rest of the word can vary.
Basically, I need to select a first word delimeted by spaces which starts with chk.
I've started with the following:
if (text.contains(" is"))
{
text.LastIndexOf(" is"); //Should give me index.
}
now I cannot find the right bound of the word since I need to match on something like
You can use regular expressions:
string pattern = #"\bis";
string input = "This isMyTest testing";
return Regex.Matches(input, pattern);
You can use IndexOf to get the index of the next space:
int startPosition = text.LastIndexOf(" is");
if (startPosition != -1)
{
int endPosition = text.IndexOf(' ', startPosition + 1); // Find next space
if (endPosition == -1)
endPosition = text.Length - 1; // Select end if this is the last word?
}
What about using a regex match? Generally if you are searching for a pattern in a string (ie starting with a space followed by some other character) regex are perfectly suited to this. Regex statements really only fall apart in contextually sensitive areas (such as HTML) but are perfect for a regular string search.
// First we see the input string.
string input = "/content/alternate-1.aspx";
// Here we call Regex.Match.
Match match = Regex.Match(input, #"[ ]is[A-z0-9]*", RegexOptions.IgnoreCase);
// Here we check the Match instance.
if (match.Success)
{
// Finally, we get the Group value and display it.
string key = match.Groups[1].Value;
Console.WriteLine(key);
}
I'm not an expert in regular expressions and today in my project I face the need to split long string in several lines in order to check if the string text fits the page height.
I need a C# regular expression to split long strings in several lines by "\n", "\r\n" and keeping 150 characters by line maximum. If the character 150 is in the middle of an word, the entire word should be move to the next line.
Can any one help me?
It's actually a quite simple problem. Look for any characters up to 150, followed by a space. Since Regex is greedy by nature it will do exactly what you want it to. Replace it by the Match plus a newline:
.{0,150}(\s+|$)
Replace with
$0\r\n
See also: http://regexhero.net/tester/?id=75645133-1de2-4d8d-a29d-90fff8b2bab5
var regex = new Regex(#".{0,150}", RegexOptions.Multiline);
var strings = regex.Replace(sourceString, "$0\r\n");
Here you go:
^.{1,150}\n
This will match the longest initial string like this.
if you just want to split a long string into lines of 150 chars then I'm not sure why you'd need a regular expression:
private string stringSplitter(string inString)
{
int lineLength = 150;
StringBuilder sb = new StringBuilder();
while (inString.Length > 0)
{
var curLength = inString.Length >= lineLength ? lineLength : inString.Length;
var lastGap = inString.Substring(0, curLength).LastIndexOfAny(new char[] {' ', '\n'});
if (lastGap == -1)
{
sb.AppendLine(inString.Substring(0, curLength));
inString = inString.Substring(curLength);
}
else
{
sb.AppendLine(inString.Substring(0, lastGap));
inString = inString.Substring(lastGap + 1);
}
}
return sb.ToString();
}
edited to account for word breaks
This code should help you. It will check the length of the current string. If it is greater than your maxLength (150) in this case, it will start at the 150th character and (going backwards) find the first non-word character (as described by the OP, this is a sequence of non-space characters). It will then store the string up to that character and start over again with the remaining string, repeating until we end up with a substring that is less than maxLength characters. Finally, join them all back together again in a final string.
string line = "This is a really long run-on sentence that should go for longer than 150 characters and will need to be split into two lines, but only at a word boundary.";
int maxLength = 150;
string delimiter = "\r\n";
List<string> lines = new List<string>();
// As long as we still have more than 'maxLength' characters, keep splitting
while (line.Length > maxLength)
{
// Starting at this character and going backwards, if the character
// is not part of a word or number, insert a newline here.
for (int charIndex = (maxLength); charIndex > 0; charIndex--)
{
if (char.IsWhiteSpace(line[charIndex]))
{
// Split the line after this character
// and continue on with the remainder
lines.Add(line.Substring(0, charIndex+1));
line = line.Substring(charIndex+1);
break;
}
}
}
lines.Add(line);
// Join the list back together with delimiter ("\r\n") between each line
string final = string.Join(delimiter , lines);
// Check the results
Console.WriteLine(final);
Note: If you run this code in a console application, you may want to change "maxLength" to a smaller number so that the console doesn't wrap on you.
Note: This code does not take into effect any tab characters. If tabs are also included, your situation gets a bit more complicated.
Update: I fixed a bug where new lines were starting with a space.
Here is what I'm trying to accomplish. I have an object coming back from
the database with a string description. This description can be up to 1000
characters long, but we only want to display a short view of this. So I coded
up the following, but I'm having trouble in actually removing the number of
words after the regular expression finds the total count of words. Does anyone
have good way of dispalying the words which are less than the Regex.Matches?
Thanks!
if (!string.IsNullOrEmpty(myObject.Description))
{
string original = myObject.Description;
MatchCollection wordColl = Regex.Matches(original, #"[\S]+");
if (wordColl.Count < 70) // 70 words?
{
uxDescriptionDisplay.Text =
string.Format("<p>{0}</p>", myObject.Description);
}
else
{
string shortendText = original.Remove(200); // 200 characters?
uxDescriptionDisplay.Text =
string.Format("<p>{0}</p>", shortendText);
}
}
EDIT:
So this is what I got working on my own:
else
{
int count = 0;
StringBuilder builder = new StringBuilder();
string[] workingText = original.Split(' ');
foreach (string word in workingText)
{
if (count < 70)
{
builder.AppendFormat("{0} ", word);
}
count++;
}
string shortendText = builder.ToString();
}
It's not pretty, but it worked. I would call it a pretty naive way of doing this. Thanks for all of the suggestions!
I would opt to go by a strict character count rather than a word count because you might happen to have a lot of long words.
I might do something like (pseudocode)
if text.Length > someLimit
find first whitespace after someLimit (or perhaps last whitespace immediately before)
display substring of text
else
display text
Possible code implementation:
string TruncateText(string input, int characterLimit)
{
if (input.Length > characterLimit)
{
// find last whitespace immediately before limit
int whitespacePosition = input.Substring(0, characterLimit).LastIndexOf(" ");
// or find first whitespace after limit (what is spec?)
// int whitespacePosition = input.IndexOf(" ", characterLimit);
if (whitespacePosition > -1)
return input.Substring(0, whitespacePosition);
}
return input;
}
One method, if you're using at least C#3.0, would be a LINQ like the following. This is provided you're going strictly by word count, not character count.
if (wordColl.Count > 70)
{
foreach (var subWord in wordColl.Cast<Match>().Select(r => r.Value).Take(70))
{
//Build string here out of subWord
}
}
I did a test using a simple Console.WriteLine with your Regex and your question body (which is over 70 words, it turns out).
You can use Regex Capture Groups to hold the match and access it later.
For your application, I'd recommend instead simply splitting the string by spaces and returning the first n elements of the array:
if (!string.IsNullOrEmpty(myObject.Description))
{
string original = myObject.Description;
string[] words = original.Split(' ');
if (words.Length < 70)
{
uxDescriptionDisplay.Text =
string.Format("<p>{0}</p>", original);
}
else
{
string shortDesc = string.Empty;
for(int i = 0; i < 70; i++) shortDesc += words[i] + " ";
uxDescriptionDisplay.Text =
string.Format("<p>{0}</p>", shortDesc.Trim());
}
}
Are you wanting to remove 200 characters or start truncating at the 200th character? When you call original.Remove(200) you are indexing the start of the truncation at the 200th character. This is how you use Remove() for a certain number of characters to remove:
string shortendText = original.Remove(0,200);
This starts at the first character and removes 200 starting with that one. Which I imagine that's not what you're trying to do since you're shortening a description. That's merely the correct way to use Remove().
Instead of using Regex matchcollections why not just split the string? It's a lot easier and straight forward. You can set the delimiter to a space character and split that way. Not sure if that completely fixes your need but it just might. I'm not sure what your data looks like in the description. But you split this way:
String[] wordArray = original.Split(' ');
From there you can determine the word count with wordArray's Length property value.
If I was you I would go by characters as you may have many one letter words or many long words in your text.
Go through until characters <= your limit, then either find the next space and then add these characters to a new string (possibly using the SubString method) or take these characters and add a few full stops, then make a new string The later could be unproffessional I suppose.