Word wrap to X lines instead of maximum width (Least raggedness)

Question

Does anyone know a good algorithm to word wrap an input string to a specified number of lines rather than a set width. Basically to achieve the minimum width for X lines.

Answer 1

btilly has the right answer here, but just for fun I decided to code up a solution in python:

def wrap_min_width(words, n):
    r, l = [], ""
    for w in words:
        if len(w) + len(l) > n:
            r, l = r + [l], ""
        l += (" " if len(l) > 0 else "") + w
    return r + [l]  

def min_lines(phrase, lines):
    words = phrase.split(" ")
    hi, lo = sum([ len(w) for w in words ]), min([len(w) for w in words])
    while lo < hi:
        mid = lo + (hi-lo)/2
        v = wrap_min_width(words, mid)
        if len(v) > lines:
            lo = mid + 1
        elif len(v) <= lines:
            hi = mid
    return lo, "\n".join(wrap_min_width(words, lo))

Now this still may not be exactly what you want, since if it is possible to wrap the words in fewer than n lines using the same line width, it instead returns the smallest number of lines encoding. (Of course you can always add extra empty lines, but it is a bit silly.) If I run it on your test case, here is what I get:

Case: "I would like to be wrapped into three lines", 3 lines

Result: 14 chars/line

I would like to

be wrapped into

three lines