51 lines
1.2 KiB
Markdown
51 lines
1.2 KiB
Markdown
---
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title: leetcode-number-of-islands
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date: 2020-04-21 12:55:17
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tags:
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- leetcode
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categories: leetcode
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---
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### 200. 岛屿数量
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[题目](https://leetcode-cn.com/problems/number-of-islands/)
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<!--more-->
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这种矩阵题现在第一反应就是用[广度优先搜索][0]做，类似之前算和0之间的距离那题。遍历矩阵，遇到 1 就将 1 改成 0，然后广度优先搜索找出 1 相邻的所有 1，这就是一个岛屿，以此类推。
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```python
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import collections
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class Solution:
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def numIslands(self, grid) -> int:
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rows = len(grid)
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if not rows:
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return 0
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cols = len(grid[0])
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islands = 0
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for r in range(rows):
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for l in range(cols):
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if grid[r][l] == '1':
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islands += 1
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grid[r][l] = '0'
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neighbors = collections.deque([(r, l)])
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while neighbors:
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x, y = neighbors.popleft()
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for x_, y_ in [[x-1, y], [x+1, y], [x, y-1], [x, y+1]]:
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if 0<=x_<rows and 0<=y_<cols and grid[x_][y_] == '1':
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neighbors.append([x_, y_])
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grid[x_][y_] = '0'
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return islands
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```
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[0]:(https://zh.wikipedia.org/zh-cn/%E5%B9%BF%E5%BA%A6%E4%BC%98%E5%85%88%E6%90%9C%E7%B4%A2)
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