#rprocon I問題を解いてみた ※まちがいだらけ

pI.py

def solve(before, after):
  pairs_dict = {}
  for i in xrange(len(before)):
    if not pairs_dict.has_key(before[i]):
      pairs_dict[before[i]] = after[i]
    else:
      if pairs_dict[before[i]] != after[i]:
        return "impossible"

  if len(pairs_dict) >= 26:
    return "impossible"

  swap_count = 0
  for k, v in pairs_dict.items():
    if pairs_dict[k] == v:
      if pairs_dict.has_key(v) and pairs_dict[v] == k:
        swap_count += 1
  swap_count /= 2

  return str(len(pairs_dict) + swap_count)


if __name__ == "__main__":
  with open('inputI.txt', 'r') as infile, open('outputI.txt', 'w') as outfile:
    data = []
    for line in infile:
      data.append(line.split())

    num = data.pop(0)
    num = int(num[0])

    for _ in xrange(num):
      [before_word] = data.pop(0)
      [after_word] = data.pop(0)
      outfile.write(solve(before_word, after_word) + '\n')