palindrome finder

palindrome_finder.rb

# Finds longest palindromic substring in O(m*n) time
def find_longest_palindrome(string)
matrix, s, size = {}, string.reverse, string.size
  0.upto(size-1) do |x|
    0.upto(size-1) do |y|
      matrix[[x,y]] = (matrix[[x-1,y-1]] || 0) + 1 if string[x] == s[y]
    end
  end
  string[matrix.key(m=matrix.values.max).first-m+1, m]
end