Time: 42 ms (98.41%), Space: 18.5 MB (34.38%) - LeetHub

0042-trapping-rain-water/0042-trapping-rain-water.py

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+class Solution:
+    def trap(self, height: List[int]) -> int:
+        left = [0] * len(height)
+        right = [0] * len(height)
+
+        waterGathered = 0
+        for i in range(len(height)):
+            if i > 0:
+                left[i] = max(left[i-1], height[i-1])
+
+            backI = len(height) - i - 1
+            if backI < len(height) - 1:
+                right[backI] = max(right[backI + 1], height[backI + 1])
+        
+        for i in range(len(height)):
+            waterGathered += max(0, min(left[i], right[i]) - height[i])
+
+        return waterGathered