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68 lines
2.6 KiB
Plaintext
68 lines
2.6 KiB
Plaintext
---
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title: '417. Pacific Atlantic Water Flow'
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description: There is an m x n rectangular island that borders both the Pacific Ocean and Atlantic Ocean. The Pacific Ocean touches the island's left and top edges, and the Atlantic Ocean touches the island's right and bottom edges
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sidebar:
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label: 'Pacific Atlantic Water Flow'
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badge: 'Medium'
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---
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<Badge variant="accent">Array</Badge>
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### Example 1:
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- Input: `heights = [[1,2,2,3,5],[3,2,3,4,4],[2,4,5,3,1],[6,7,1,4,5],[5,1,1,2,4]]`
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- Output: `[[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]`
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- Explanation: The following cells can flow to the Pacific and Atlantic oceans, as shown below: `[0,4]`: `[0,4]` -> Pacific Ocean `[0,4]` -> Atlantic Ocean `[1,3]`: `[1,3]` -> `[0,3]` -> Pacific Ocean `[1,3]` -> `[1,4]` -> Atlantic Ocean `[1,4]`: `[1,4]` -> `[1,3]` -> `[0,3]` -> Pacific Ocean `[1,4]` -> Atlantic Ocean `[2,2]`: `[2,2]` -> `[1,2]` -> `[0,2]` -> Pacific Ocean `[2,2]` -> `[2,3]` -> `[2,4]` -> Atlantic Ocean `[3,0]`: `[3,0]` -> Pacific Ocean `[3,0]` -> `[4,0]` -> Atlantic Ocean `[3,1]`: `[3,1]` -> `[3,0]` -> Pacific Ocean `[3,1]` -> `[4,1]` -> Atlantic Ocean `[4,0]`: `[4,0]` -> Pacific Ocean `[4,0]` -> Atlantic Ocean Note that there are other possible paths for these cells to flow to the Pacific and Atlantic oceans.
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### Example 2:
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- Input: `heights = [[1]]`
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- Output: `[[0,0]]`
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- Explanation: The water can flow from the only cell to the Pacific and Atlantic oceans.
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### Constraints:
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- `m == heights.length`
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- `n == heights[r].length`
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- `1 <= m, n <= 200`
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- `0 <= heights[r][c] <= 10^5`
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## Solution
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```py
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class Solution:
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def pacificAtlantic(self, heights: list[list[int]]) -> list[list[int]]:
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rows, cols = len(heights), len(heights[0])
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pac, atl = set(), set()
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def dfs(r, c, seen, prevHeight):
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if (
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(r, c) in seen
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or r < 0
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or c < 0
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or r == rows
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or c == cols
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or heights[r][c] < prevHeight
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):
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return
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seen.add((r, c))
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dfs(r + 1, c, seen, heights[r][c])
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dfs(r - 1, c, seen, heights[r][c])
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dfs(r, c + 1, seen, heights[r][c])
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dfs(r, c - 1, seen, heights[r][c])
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for c in range(cols):
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dfs(0, c, pac, heights[0][c])
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dfs(rows - 1, c, atl, heights[rows - 1][c])
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for r in range(rows):
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dfs(r, 0, pac, heights[r][0])
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dfs(r, cols - 1, atl, heights[r][cols - 1])
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res = []
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for r in range(rows):
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for c in range(cols):
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if (r, c) in pac and (r, c) in atl:
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res.append([r, c])
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return res
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```
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