Codeforces Round #222 (Div. 2) C. Maze 解けない。

maze.py

import Queue

def solve(k, strs):
  strsX = []
  for str in strs:
    strsX.append(list(str.replace('.', 'X')))

  num_X = countX(strsX)
  strsX = replaceX(strsX, num_X - k)

  for str in strsX:
    print ''.join(str)



def replaceX(strs, num):
  candis = [(0, 1), (1, 0), (0, -1), (-1, 0)]
  queue = Queue.deque()
  queue.append(firstX(strs))
  visited = []
  while num > 0 and queue:
    q = queue.pop()
    x, y = q[0], q[1]
    strs[x][y] = '.'
    num -= 1

    for candi in candis:
      nx, ny = x + candi[0], y + candi[1]
      if 0 <= nx < len(strs) and 0 <= ny < len(strs[0]):
        if strs[nx][ny] == 'X' and (nx, ny) not in visited:
          queue.append((nx, ny))
          visited.append((nx, ny))
  return strs


def countX(str):
  counter = 0
  for i in xrange(len(str)):
    for j in xrange(len(str[i])):
      if str[i][j] == 'X':
        counter += 1
  return counter

def firstX(str):
  for i in xrange(len(str)):
    for j in xrange(len(str[i])):
      if str[i][j] == 'X':
        return (i, j)


if __name__ == "__main__":
  n, m, k = map(int, raw_input().split())
  strs = []
  for i in xrange(n):
    strs.append(raw_input())
  solve(k, strs)