[LeetCode Sync] Runtime - 132 ms (51.86%), Memory - 20.1 MB (81.51%)

Author: NamVr

0407-trapping-rain-water-ii/solution.py

@@ -0,0 +1,41 @@
+class Solution:
+    def trapRainWater(self, heightMap: List[List[int]]) -> int:
+        if not heightMap or not heightMap[0]:
+            return 0
+			
+			
+		# Initial
+		# Board cells cannot trap the water
+        m, n = len(heightMap), len(heightMap[0])
+        if m < 3 or n < 3:
+            return 0
+			
+			
+		# Add Board cells first
+        heap = []
+        for i in range(m):
+            for j in range(n):
+                if i == 0 or i == m - 1 or j == 0 or j == n - 1:
+                    heapq.heappush(heap, (heightMap[i][j], i, j))
+                    heightMap[i][j] = -1
+					
+					
+		# Start from level 0
+        level, res = 0, 0
+        
+        while heap:
+            height, x, y = heapq.heappop(heap)
+            level = max(height, level)
+
+            for i, j in [(x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)]:
+                if 0 <= i < m and 0 <= j < n and heightMap[i][j] != -1:
+                    heapq.heappush(heap, (heightMap[i][j], i, j))
+					
+					# If cell's height smaller than the level, then it can trap the rain water
+                    if heightMap[i][j] < level:
+                        res += level - heightMap[i][j]
+						
+					# Set the height to -1 if the cell is visited
+                    heightMap[i][j] = -1
+
+        return res