How to split string preserving whole words?

Question

I need to split long sentence into parts preserving whole words. Each part should have given maximum number of characters (including space, dots etc.). For example:

Answer 1

Expanding on jon's answer above; I needed to switch g with g.toArray(), and also change max to (max + 2) to get an exact wrapping on the max'th character.

public static class ExtensionMethods
{
    public static string[] Wrap(this string text, int max)
    {
        var charCount = 0;
        var lines = text.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
        return lines.GroupBy(w => (charCount += w.Length + 1) / (max + 2))
                    .Select(g => string.Join(" ", g.ToArray()))
                    .ToArray();
    }
}

And here is sample usage as NUnit tests:

[Test]
public void TestWrap()
{
    Assert.AreEqual(2, "A B C".Wrap(4).Length);
    Assert.AreEqual(1, "A B C".Wrap(5).Length);

    Assert.AreEqual(2, "AA BB CC".Wrap(7).Length);
    Assert.AreEqual(1, "AA BB CC".Wrap(8).Length);

    Assert.AreEqual(2, "TEST TEST TEST TEST".Wrap(10).Length);
    Assert.AreEqual(2, "  TEST TEST TEST TEST  ".Wrap(10).Length);
    Assert.AreEqual("TEST TEST", "  TEST TEST TEST TEST  ".Wrap(10)[0]);
}

Answer 2

While CsConsoleFormat† was primarily designed to format text for console, it supports generating plain text as well.

var doc = new Document().AddChildren(
  new Div("Silver badges are awarded for longer term goals. Silver badges are uncommon.") {
    TextWrap = TextWrapping.WordWrap
  }
);
var bounds = new Rect(0, 0, 35, Size.Infinity);
string text = ConsoleRenderer.RenderDocumentToText(doc, new TextRenderTarget(), bounds);

And, if you actually need trimmed strings like in your question:

List<string> lines = text.Trim()
  .Split(new[] { Environment.NewLine }, StringSplitOptions.None)
  .Select(s => s.Trim())
  .ToList();

In addition to word wrap on spaces, you get proper handling of hyphens, zero-width spaces, no-break spaces etc.

_{† CsConsoleFormat was developed by me.}

Answer 3

I knew there had to be a nice LINQ-y way of doing this, so here it is for the fun of it:

var input = "The quick brown fox jumps over the lazy dog.";
var charCount = 0;
var maxLineLength = 11;

var lines = input.Split(' ', StringSplitOptions.RemoveEmptyEntries)
    .GroupBy(w => (charCount += w.Length + 1) / maxLineLength)
    .Select(g => string.Join(" ", g));

// That's all :)

foreach (var line in lines) {
    Console.WriteLine(line);
}

Obviously this code works only as long as the query is not parallel, since it depends on charCount to be incremented "in word order".

Answer 4

Split the string with a (space), that build up new strings from the resulting array, stopping before your limit for each new segment.

Untested pseudo-code:

string[] words = sentence.Split(new char[] {' '});
IList<string> sentenceParts = new List<string>();
sentenceParts.Add(string.Empty);

int partCounter = 0;    

foreach (var word in words)
{
  if(sentenceParts[partCounter].Length + word.Length > myLimit)
  {
     partCounter++;
     sentenceParts.Add(string.Empty);
  }

  sentenceParts[partCounter] += word + " ";
}

Answer 5

It seems like everyone is using some form of "Split then rebuild the sentence"...

I thought I would take a stab at this the way my brain would logically think about doing this manually, which is:

• Split on length
• Go backwards to the nearest space and use that chunk
• Remove the used chunk and start over

The code ended up being a little more complex than I was hoping for, however I believe it handles most (all?) edge cases - including words that are longer than maxLength, when the words end exactly on the maxLength, etc.

Here's my function:

private static List<string> SplitWordsByLength(string str, int maxLength)
{
    List<string> chunks = new List<string>();
    while (str.Length > 0)
    {
        if (str.Length <= maxLength)                    //if remaining string is less than length, add to list and break out of loop
        {
            chunks.Add(str);
            break;
        }

        string chunk = str.Substring(0, maxLength);     //Get maxLength chunk from string.

        if (char.IsWhiteSpace(str[maxLength]))          //if next char is a space, we can use the whole chunk and remove the space for the next line
        {
            chunks.Add(chunk);
            str = str.Substring(chunk.Length + 1);      //Remove chunk plus space from original string
        }
        else
        {
            int splitIndex = chunk.LastIndexOf(' ');    //Find last space in chunk.
            if (splitIndex != -1)                       //If space exists in string,
                chunk = chunk.Substring(0, splitIndex); //  remove chars after space.
            str = str.Substring(chunk.Length + (splitIndex == -1 ? 0 : 1));      //Remove chunk plus space (if found) from original string
            chunks.Add(chunk);                          //Add to list
        }
    }
    return chunks;
}

Test usage:

string testString = "Silver badges are awarded for longer term goals. Silver badges are uncommon.";
int length = 35;

List<string> test = SplitWordsByLength(testString, length);

foreach (string chunk in test)
{
    Console.WriteLine(chunk);  
}

Console.ReadLine();

Answer 6

At first I was thinking this might be a Regex kind of thing but here's my shot at it:

List<string> parts = new List<string>();
int partLength = 35;
string sentence = "Silver badges are awarded for longer term goals. Silver badges are uncommon.";

string[] pieces = sentence.Split(' ');
StringBuilder tempString = new StringBuilder("");

foreach(var piece in pieces)
{
    if(piece.Length + tempString.Length + 1 > partLength) 
    {
        parts.Add(tempString.ToString());
        tempString.Clear();        
    }
    tempString.Append(" " + piece); 
}