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200.py
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200.py
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class Solution(object):
def numIslands(self, grid):
"""
:type grid: List[List[str]]
:rtype: int
"""
if not grid:
return 0
ans = 0
for i in range(m):
for j in range(n):
if grid[i][j] == '1':
self.helper(grid, i, j)
ans += 1
return ans
# 不知道为什么内联性的helper会超过递归栈 -> 是我代码写错了
# 小窍门,改grid从而省去visit
def helper(self, grid, x, y):
if x<0 or x>=len(grid) or y<0 or y>=len(grid[0]) or grid[x][y] != '1':
return
grid[x][y] = '#'
dire = [[1, 0], [-1, 0], [0, 1], [0, -1]]
for i in range(4):
self.helper(grid, x+dire[i][0], y+dire[i][1])
class Solution(object):
def numIslands(self, grid):
"""
:type grid: List[List[str]]
:rtype: int
"""
if not grid:
return 0
if not grid[0]:
return 0
m, n = len(grid), len(grid[0])
visit = [[0]*n for i in range(m)]
def helper(x, y):
# 这里除了visit之外没有判断grid为0的地方,导致无穷递归
if x<0 or x>=m or y<0 or y>= n or visit[x][y] == 1 or grid[x][y]=='0':
return
visit[x][y] = 1
helper(x + 1, y)
helper(x - 1, y)
helper(x, y + 1)
helper(x, y - 1)
ans = 0
for i in range(m):
for j in range(n):
if grid[i][j] == '1' and visit[i][j] == 0:
helper(i,j)
ans += 1
return ans