Split large text string into variable length strings without breaking words and keeping linebreaks and spaces

Question

I am trying to break a large string of text into several smaller strings of text and define each smaller text strings max length to be different. for example:

"The quick brown fox jumped over the red fence.
       The blue dog dug under the fence."

I would like to have code that can split this into smaller lines and have the first line have a max of 5 characters, the second line have a max of 11, and rest have a max of 20, resulting in this:

Line 1: The 
Line 2: quick brown
Line 3: fox jumped over the 
Line 4: red fence.
Line 5:        The blue dog 
Line 6: dug under the fence.

All this in C# or MSSQL, is it possible?

Answer 1

public List<String> SplitString(String text, int [] lengths)
{
   List<String> output = new List<String>();

   List<String> words = Split(text);

   int i = 0;
   int lineNum = 0;
   string s = string.empty;
   while(i<words.Length)
   {
       if(s.Length+words[i].Length <lengths[lineNum])
       {
            s+=words[i];
            i++;
            if(lineNum<lengths.Length-1)
                 lineNum++;
       }
       else
       {
          output.Add(s);
          s=String.Empty;
       }

   }

    s.Remove(S.length-1,1);// deletes last extra space.

    return output;
}


   public static List<string> Split(string text)
    {
        List<string> result = new List<string>();
        StringBuilder sb = new StringBuilder();

        foreach (var letter in text)
        {
            if (letter != ' ' && letter != '\t' && letter != '\n')
            {
                sb.Append(letter);
            }
            else
            {
                if (sb.Length > 0)
                {

                    result.Add(sb.ToString());
                }

                result.Add(letter.ToString());
                sb = new StringBuilder();
            }
        }

        return result;
    }

This is untested/compiled code, but you should get the idea.

I also think you should use a StringBuilder instead, but I didn't remember how to use it.

Answer 2

\A(.{0,5}\b)(.{0,11}\b)(.{0,20}\b)+\Z

will capture up to five characters in group 1, up to 11 in group 2 and chunks of up to 20 in group 3. Matches will be split along word delimiters in order to avoid splitting in the middle of a word. Whitespace, line break etc. count as characters and will be preserved.

The trick is to get at the individual matches in the repeated group, something that can only be done in .NET and Perl 6:

Match matchResults = null;
Regex paragraphs = new Regex(@"\A(.{0,5}\b)(.{0,11}\b)(.{0,20}\b)+\Z", RegexOptions.Singleline);
matchResults = paragraphs.Match(subjectString);
if (matchResults.Success) {
    String line1 = matchResults.Groups[1].Value;
    String line2 = matchResults.Groups[2].Value;
    Capture line3andup = matchResults.Groups[3].Captures;
    // you now need to iterate over line3andup, extracting the lines.
} else {
    // Match attempt failed
} 

I don't know C# at all and have tried to construct this from RegexBuddy's templates and the VB code here, so please feel free to point out my coding errors.

Note that the whitespace at the beginning of line two is captured at the end of the previous match.