Divide long string into 60 character long lines but don't break words

Question

There has to be a better way to do this. I just want to split long string into 60 character lines but do not break words. So it doesn't have to add up to 60 characters just has to be less than 60.

The code below is what I have and it works but I'm thinking there's a better way. Anybody?

Modified to use StringBuilder and fixed the problem of removing a repeating word. Also don't want to use regex because I think that would be less efficient than what I have now.

public static List<String> FormatMe(String Message)
{
    Int32 MAX_WIDTH = 60;
    List<String> Line = new List<String>();
    String[] Words;

    Message = Message.Trim();
    Words = Message.Split(" ".ToCharArray());

    StringBuilder s = new StringBuilder();
    foreach (String Word in Words)
    {
        s.Append(Word + " ");
        if (s.Length > MAX_WIDTH)
        {
            s.Replace(Word, "", 0, s.Length - Word.Length);
            Line.Add(s.ToString().Trim());
            s = new StringBuilder(Word + " ");
        }
    }

    if (s.Length > 0)
        Line.Add(s.ToString().Trim());

    return Line;
}

Thanks

Answer 1

Another (now TESTED) sample, very similiar to Keith approach:

static void Main(string[] args)
{
    const Int32 MAX_WIDTH = 60;

    int offset = 0;
    string text = Regex.Replace(File.ReadAllText("oneline.txt"), @"\s{2,}", " ");
    List<string> lines = new List<string>();
    while (offset < text.Length)
    {
        int index = text.LastIndexOf(" ", 
                         Math.Min(text.Length, offset + MAX_WIDTH));
        string line = text.Substring(offset,
            (index - offset <= 0 ? text.Length : index) - offset );
        offset += line.Length + 1;
        lines.Add(line);
    }
}

I ran that on this file with all line breaks manually replaced by " ".

Answer 2

Try this:

const Int32 MAX_WIDTH = 60;

string text = "...";
List<string> lines = new List<string>();
StringBuilder line = new StringBuilder();
foreach(Match word in Regex.Matches(text, @"\S+", RegexOptions.ECMAScript))
{
    if (word.Value.Length + line.Length + 1 > MAX_WIDTH)
    {
        lines.Add(line.ToString());
        line.Length = 0;
    }
    line.Append(String.Format("{0} ", word.Value));
}

if (line.Length > 0)
    line.Append(word.Value);

Please, also check this out: How do I use a regular expression to add linefeeds?

Answer 3

Inside a Regular expression, the Match Evaluator function (an anonymous method) does the grunt work and stores the newly sized lines into a StringBuilder. We don't use the return value of Regex.Replace method because we're just using its Match Evaluator function as a feature to accomplish line breaking from inside the regular expression call - just for the heck of it, because I think it's cool.

using System;
using System.Text;
using System.Text.RegularExpressions;

strInput is what you want to convert the lines of.

int MAX_LEN = 60;
StringBuilder sb = new StringBuilder();
int bmark = 0; //bookmark position

Regex.Replace(strInput, @".*?\b\w+\b.*?", 
    delegate(Match m) {
        if (m.Index - bmark + m.Length + m.NextMatch().Length > MAX_LEN 
                || m.Index == bmark && m.Length >= MAX_LEN) {
            sb.Append(strInput.Substring(bmark, m.Index - bmark + m.Length).Trim() + Environment.NewLine);
            bmark = m.Index + m.Length;
        } return null;
    }, RegexOptions.Singleline);

if (bmark != strInput.Length) // last portion
    sb.Append(strInput.Substring(bmark));

string strModified = sb.ToString(); // get the real string from builder

It's also worth noting the second condition in the if expression in the Match Evaluator m.Index == bmark && m.Length >= MAX_LEN is meant as an exceptional condition in case there is a word longer than 60 chars (or longer than the set max length) - it will not be broken down here but just stored on one line by itself - I guess you might want to create a second formula for that condition in the real world to hyphenate it or something.

Answer 4

An other one ...

public static string SplitLongWords(string text, int maxWordLength)
{
    var reg = new Regex(@"\S{" + (maxWordLength + 1) + ",}");
    bool replaced;
    do
    {
        replaced = false;
        text = reg.Replace(text, (m) =>
        {
            replaced = true;
            return m.Value.Insert(maxWordLength, " ");                    
        });
    } while (replaced);

    return text;
}

Answer 5

I would start with saving the length of the original string. Then, start backwards, and just subtract, since odds are that I would get below 60 faster by starting at the last word and going back than building up.

Once I know how long, then just use StringBuilder and build up the string for the new string.

Answer 6

List<string> lines = new List<string>();
while (message.Length > 60) {
  int idx = message.LastIndexOf(' ', 60);
  lines.Add(message.Substring(0, idx));
  message = message.Substring(idx + 1, message.Length - (idx + 1));
}
lines.Add(message);

You might need to modify a bit to handle multiple spaces, words with >60 chars in them, ...

Answer 7

I tried the original solution and found that it didn't quite work. I've modified it slightly to make it work. It now works for me and solves a problem I had. Thanks. Jim.

public static List<String> FormatMe(String message)
    {
        int maxLength = 10;
        List<String> Line = new List<String>();
        String[] words;

        message = message.Trim();
        words = message.Split(" ".ToCharArray());

        StringBuilder sentence = new StringBuilder();
        foreach (String word in words)
        {
            if((sentence.Length + word.Length) <= maxLength)
            {
                sentence.Append(word + " ");

            }
            else
            {
                Line.Add(sentence.ToString().Trim());
                sentence = new StringBuilder(word + " ");
            }
        }

        if (sentence.Length > 0)
            Line.Add(sentence.ToString().Trim());

        return Line;
    }

    private void btnSplitText_Click(object sender, EventArgs e)
    {
        List<String> Line = new List<string>();
        string message = "The quick brown fox jumps over the lazy dog.";
        Line = FormatMe(message);
    }