Find the longest common starting substring in a set of strings [closed]

Answer 1

This is by no means elegant, but if you want concise:

Ruby, 71 chars

def f(a)b=a[0];b[0,(0..b.size).find{|n|a.any?{|i|i[0,n]!=b[0,n]}}-1]end

If you want that unrolled it looks like this:

def f(words)
  first_word = words[0];
  first_word[0, (0..(first_word.size)).find { |num_chars|
    words.any? { |word| word[0, num_chars] != first_word[0, num_chars] }
  } - 1]
end