Create Pacific Atlantic Water Flow - Leetcode 417.py

Author: gahogg

Pacific Atlantic Water Flow - Leetcode 417.py

@@ -0,0 +1,43 @@
+from collections import deque
+
+class Solution:
+    def pacificAtlantic(self, heights: List[List[int]]) -> List[List[int]]:
+        p_que = deque()
+        p_seen = set()
+      
+        a_que = deque()
+        a_seen = set()
+      
+        m, n = len(heights), len(heights[0])
+
+        for j in range(n):
+            p_que.append((0, j))
+            p_seen.add((0, j))
+          
+        for i in range(1, m):
+            p_que.append((i, 0))
+            p_seen.add((i, 0))
+          
+        for i in range(m):
+            a_que.append((i, n - 1))
+            a_seen.add((i, n - 1))
+          
+        for j in range(n - 1):
+            a_que.append((m - 1, j))
+            a_seen.add((m - 1, j))
+
+        def get_coords(que, seen):
+            coords = set()
+            while que:
+                i, j = que.popleft()
+                coords.add((i, j))
+                for i_off, j_off in [(0, 1), (1, 0), (-1, 0), (0, -1)]:
+                    r, c = i + i_off, j + j_off
+                    if 0 <= r < m and 0 <= c < n and heights[r][c] >= heights[i][j] and (r, c) not in seen:
+                        seen.add((r, c))
+                        que.append((r, c))
+            return coords
+
+        p_coords = get_coords(p_que, p_seen)
+        a_coords = get_coords(a_que, a_seen)
+        return list(p_coords.intersection(a_coords))