Create 417-Pacific-Atlantic-Waterflow.py

Author: neetcode-gh

417-Pacific-Atlantic-Waterflow.py

@@ -0,0 +1,30 @@
+class Solution:
+    def pacificAtlantic(self, heights: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(heights), len(heights[0])
+        pac, atl = set(), set()
+        
+        def dfs(r, c, visit, prevHeight):
+            if ((r, c) in visit or 
+               r < 0 or c < 0 or r == ROWS or c == COLS or
+               heights[r][c] < prevHeight):
+                return
+            visit.add((r, c))
+            dfs(r + 1, c, visit, heights[r][c])
+            dfs(r - 1, c, visit, heights[r][c])
+            dfs(r, c + 1, visit, heights[r][c])
+            dfs(r, c - 1, visit, heights[r][c])
+        
+        for c in range(COLS):
+            dfs(0, c, pac, heights[0][c])
+            dfs(ROWS - 1, c, atl, heights[ROWS - 1][c])
+        
+        for r in range(ROWS):
+            dfs(r, 0, pac, heights[r][0])
+            dfs(r, COLS - 1, atl, heights[r][COLS - 1])
+        
+        res = []
+        for r in range(ROWS):
+            for c in range(COLS):
+                if (r, c) in pac and (r, c) in atl:
+                    res.append([r, c])
+        return res