/
numIslands.py
executable file
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/
numIslands.py
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# -*- coding: utf-8 -*-
"""
Created on Mon Nov 19 10:31:21 2018
给一个01矩阵,求不同的岛屿的个数。
0代表海,1代表岛,如果两个1相邻,那么这两个1属于同一个岛。我们只考虑上下左右为相邻。
样例
在矩阵:
[
[1, 1, 0, 0, 0],
[0, 1, 0, 0, 1],
[0, 0, 0, 1, 1],
[0, 0, 0, 0, 0],
[0, 0, 0, 0, 1]
]
中有3个岛。
深度优先思想。遍历矩阵的每个元素,如果为1则计数加一,同时把自己和周围的元素都置0。
@author: shuping
"""
class Solution:
# @param {boolean[][]} grid a boolean 2D matrix
# @return {int} an integer
def numIslands(self, grid):
# Write your code here
if grid is None:
return None
m = len(grid)
if m == 0:
return 0
n = len(grid[0])
if n == 0:
return 0
res = 0
for i in range(m):
for j in range(n):
if grid[i][j]:
res += 1
self.dfs(grid, i, j)
return res
def dfs(self, grid, i, j):
if i < 0 or j < 0 or i >= len(grid) or j >= len(grid[0]):
return
if grid[i][j]:
grid[i][j] = 0
self.dfs(grid, i + 1, j)
self.dfs(grid, i - 1, j)
self.dfs(grid, i, j - 1)
self.dfs(grid, i, j + 1)
if __name__ == '__main__':
pass
solution = Solution()
grid = [
[1, 1, 0, 0, 0],
[0, 1, 0, 0, 1],
[0, 0, 0, 1, 1],
[0, 0, 0, 0, 0],
[0, 0, 0, 0, 1]
]
step = solution.numIslands(grid)
print(str(step))