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I'm looking to implement a way to perform text justification (flush left and right). Each output line can have a maximum width of M characters. Breaking of words is not allowed.

For example, please see "Justified (flush left and right)" in this wikipedia page: http://en.wikipedia.org/wiki/Justification_(typesetting).

I'm aware that there is a dynamic programming solution for optimal flush left, ragged right justification i.e. distribute the extra spaces at the end of the lines evenly such that the cost of extra spaces is optimal (this is also known as the 'word wrap' problem or 'printing neatly' problem). However, I'm not able to arrive at a dynamic programming or greedy approach for the full text justification problem.

Googling lead me to text justification based on Markov Chain Programming: http://www.rose-hulman.edu/Users/faculty/young/OldFiles/CS-Classes/csse220/200820/web/Programs/Markov/justification.html. But this seems complicated to me. If this is the best (and simplest) solution to the full text justification problem, then it will be great if somebody could explain the same in easy words.

Kowshik
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    Why do you even need DP? On left justification dump all the spaces on right, vice versa for right. For full, distribute spaces equally between every consecutive pair of words, no? – ElKamina Mar 27 '13 at 20:11
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    @ElKamina, I think OP wants to fully justify entire multi-line paragraphs, rather than single lines. So the question is how to produce an "optimal" distribution of white space, for some definition of optimality. At least, I hope that's it, because, as you say, the problem is otherwise trivial. – rici Mar 27 '13 at 20:26
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    Kowshik, breaking lines so that there is an even distribution of spaces at the end of lines is pretty well the best way of breaking lines for full justification, too. Once you've broken the lines, you then distribute the extra space for each line "as evenly as possible" between the words on that line (except for the last line of a paragraph). Is there something more subtle you wanted to know? Lots of references here: http://en.wikipedia.org/wiki/Word_wrap – rici Mar 27 '13 at 20:32
  • @rici What I would like to arrive at is a solution to the problem that maintains a constant distribution of white spaces between any two words on the same line in the entire justified paragraph. If no such solution exists, then we can distribute the extra space as evenly as possible. Do you think this change to the original question makes sense? This layout yields a better look to the justified text, but in most practical cases your solution works fine. – Kowshik Mar 27 '13 at 20:50
  • OK, I think you need to add that optimization criterion to your question. In fact, you should rewrite the question based on that criterion, so as to distinguish it from any other solution (minimum raggedness, for example). I think you'll be able to find a Knuth-Plass-like solution (the dynamic programming algorithm), but don't expect it to be trivial. The Markov chain thing is a red herring; it's someone trying to come up with a simple exercise to teach Markov chains; not someone proposing a solution to paragraph formatting. – rici Mar 27 '13 at 22:59

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