pacific-atlantic-water-flow solution

Author: devyejin

pacific-atlantic-water-flow/devyejin.py

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+from typing import List
+from collections import deque
+
+# time O(mn), saoce O(mn)
+class Solution:
+    def pacificAtlantic(self, heights: List[List[int]]) -> List[List[int]]:
+        m, n = len(heights), len(heights[0])
+        # 방문 배열
+        pacific = [[False] * n for _ in range(m)]
+        atlantic = [[False] * n for _ in range(m)]
+
+        directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+
+        def bfs(r, c, visited):
+            queue = deque([(r, c)])
+            visited[r][c] = True
+
+            while queue:
+                r, c = queue.popleft()
+
+                for dr, dc in directions:
+                    new_r, new_c = r + dr, c + dc
+                    if (0 <= new_r < m and 0 <= new_c < n
+                            and not visited[new_r][new_c]
+                            and heights[new_r][new_c] >= heights[r][c]):
+                        visited[new_r][new_c] = True
+                        queue.append((new_r, new_c))
+
+        for i in range(n):
+            bfs(0, i, pacific)
+            bfs(m - 1, i, atlantic)
+        for i in range(m):
+            bfs(i, 0, pacific)
+            bfs(i, n - 1, atlantic)
+
+        result = []
+        for i in range(m):
+            for j in range(n):
+                if pacific[i][j] and atlantic[i][j]:
+                    result.append([i, j])
+
+        return result
+
+
+