def wordladder(strings): def wordladderRecu(strings, used, cur, length): if len(cur) == length: return 1 for i in xrange(length): if not cur or (not used[i] and strings[i][0] == cur[-1][len(cur[-1])-1]): used[i] = True cur.append(strings[i]) result = wordladderRecu(strings, used, cur, length) cur.pop(-1) used[i] = False if result: return 1 return 0 length = len(strings) used = [False]*length return wordladderRecu(strings, used, [], length) if __name__=="__main__": print wordladder(["hello","world","open","dog","now"]) print wordladder(["dog","world"]) print wordladder(["hello","world"])