Solve : Pacific Atlantic Water Flow

Author: printjin-gmailcom

pacific-atlantic-water-flow/printjin-gmailcom.py

@@ -0,0 +1,25 @@
+class Solution:
+    def pacificAtlantic(self, heights):
+        if not heights:
+            return []
+        m, n = len(heights), len(heights[0])
+        pacific = [[False] * n for _ in range(m)]
+        atlantic = [[False] * n for _ in range(m)]
+        def dfs(r, c, visited):
+            visited[r][c] = True
+            for dr, dc in [(-1,0), (1,0), (0,-1), (0,1)]:
+                nr, nc = r + dr, c + dc
+                if 0 <= nr < m and 0 <= nc < n and not visited[nr][nc] and heights[nr][nc] >= heights[r][c]:
+                    dfs(nr, nc, visited)
+        for i in range(m):
+            dfs(i, 0, pacific)
+            dfs(i, n - 1, atlantic)
+        for j in range(n):
+            dfs(0, j, pacific)
+            dfs(m - 1, j, atlantic)
+        result = []
+        for r in range(m):
+            for c in range(n):
+                if pacific[r][c] and atlantic[r][c]:
+                    result.append([r, c])
+        return result