Cut the string to be <= 80 characters AND must keep the words without cutting them

Question

I am new to C#, but I have a requirement to cut the strings to be <= 80 characters AND they must keep the words integrity (without cutting them)

Examples

Before: I have a requirenment to cut the strings to be <= 80 characters AND must keep the words without cutting them (length=108)
After: I have a requirenment to cut the strings to be <= 80 characters AND must keep (length=77)

Before: requirenment to cut the strings to be <= 80 characters AND must keep the words without cutting them (length=99)
After: requirenment to cut the strings to be <= 80 characters AND must keep the words (length=78)

Before: I have a requirenment the strings to be <= 80 characters AND must keep the words without cutting them (length=101)
After: I have a requirenment the strings to be <= 80 characters AND must keep the words (length=80)

I want to use the RegEx, but I don't know anything about the regex. It would be a hassle to to the else-if's for this. I would appreciate if you could point me to the right article which I could use to create this expression.

this is my function that I want to cut to one line:

public String cutTitleto80(String s){
    String[] words = Regex.Split(s, "\\s+");
    String finalResult = "";
    foreach (String word in words)
    {
        String tmp = finalResult + " " + word;
        if (tmp.Length > 80)
        {
            return finalResult;
        }
        finalResult = tmp;
    }
    return finalResult;
}

[What have you tried](http://whathaveyoutried.com)? Where are you stuck? Regular expressions seem like overkill for this. — Oded, Sep 28 '12 at 19:30
I think I'd just use a split by space character, loop through the array and concatenate until I exceed 80. — ED-209, Sep 28 '12 at 19:33
@Oded I'm curious as to how you would implement this using regex *only*. — NullUserException, Sep 28 '12 at 19:33
@NullUserException - Actually, I don't think regex is suitable at all. A small parser would be a much better choice. — Oded, Sep 28 '12 at 19:34

Ben Voigt · Answer 1 · 2012-09-28T20:04:18.183

6

Try

^(.{0,80})(?: |$)

This is a capturing greedy match which must be followed by a space or end of string. You could also use a zero-width lookahead assertion, as in

^.{0,80}(?= |$)

If you use a live test tool like http://regexhero.net/tester/ it's pretty cool, you can actually see it jump back to the word boundary as you type beyond 80 characters.

And here's one which will simply truncate at the 80th character if there are no word boundaries (spaces) to be found:

^(.{1,80}(?: |$)|.{80})

edited Sep 28 '12 at 20:04

answered Sep 28 '12 at 19:45

Ben Voigt

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Somehow I forgot capture groups existed. Here, have an upboat. – NullUserException Sep 28 '12 at 19:52
@NullUserException: You could do it without groups also, by using a zero-width lookahead assertion. But the syntax for those is complicated and hurts my brain. – Ben Voigt Sep 28 '12 at 19:53

voithos · Accepted Answer · 2012-09-28T19:39:31.477

Here's an approach without using Regex: just split the string (however you'd like) into whatever you consider "words" to be. Then, just start concatenating them together using a StringBuilder, checking for your desired length, until you can't add the next "word". Then, just return the string that you have built up so far.

(Untested code ahead)

public string TruncateWithPreservation(string s, int len)
{
    string[] parts = s.Split(' ');
    StringBuilder sb = new StringBuilder();

    foreach (string part in parts)
    {
        if (sb.Length + part.Length > len)
            break;

        sb.Append(' ');
        sb.Append(part);
    }

    return sb.ToString();
}

Keith · Answer 3 · 2017-07-20T13:22:51.620

1

string truncatedText = text.Substring(0, 80);  // truncate to 80 characters
if (text[80] != ' ')  // don't remove last word if a space occurs after it in the original string (in other words, last word is already complete)
    truncatedText = truncatedText.Substring(0, truncatedText.LastIndexOf(' '));  // remove any cut-off words

Updated to fix issue from comments where last word could get cut off even if it is complete.

edited Jul 20 '17 at 13:22

answered Sep 28 '12 at 19:46

Keith

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This will remove the last word even if the string is already short enough. – Ben Voigt Sep 28 '12 at 19:48
Easy enough to add an `EndsWith(" ")` check. However, this approach will also throw an exception if there are no spaces at all! :) – Chris Sinclair Sep 28 '12 at 19:55
@Chris: I'm not sure what `EndsWith(" ")` improves. The required check would be `test.Length > 80`. – Ben Voigt Sep 28 '12 at 20:00
@BenVoigt Oops, got my wires crossed about how to check for the last word. Disregard me. :) – Chris Sinclair Sep 28 '12 at 20:19

Tom Vervoort · Answer 4 · 2012-09-28T20:04:37.317

0

This isn't using regex but this is how I would do it:

Use String.LastIndexOf to get the last space before the 81st char.
If the 81th char is a space then take it until 80.
if it returns a number > -1 cut it off there.
If it's -1 you-have-a-really-long-word-or-someone-messing-with-the-system so you do wathever you like.

edited Sep 28 '12 at 20:04

answered Sep 28 '12 at 19:43

Tom Vervoort

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Cut the string to be <= 80 characters AND must keep the words without cutting them

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