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130. Surrounded Regions.py
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130. Surrounded Regions.py
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class Solution(object):
def solve(self, board):
"""
:type board: List[List[str]]
:rtype: void Do not return anything, modify board in-place instead.
"""
if not board or not board[0]:
return
m = len(board)
n = len(board[0])
for i in xrange(m):
self.DFS(i, 0, board)
self.DFS(i, n-1, board)
for j in xrange(n):
self.DFS(0, j, board)
self.DFS(m-1, j, board)
for i in xrange(m):
for j in xrange(n):
if board[i][j] == 'O':
board[i][j] = 'X'
if board[i][j] == '*':
board[i][j] = "O"
def DFS(self, i, j, board):
m = len(board)
n = len(board[0])
queue = [(i,j)]
while queue:
(x, y) = queue.pop(0)
if x < 0 or y < 0 or x >= m or y >= n or board[x][y] != 'O':
continue
board[x][y] = '*'
queue += [(x-1, y)]
queue += [(x+1, y)]
queue += [(x, y-1)]
queue += [(x, y+1)]