Solution for problem 42 with Python

Hard/42. Trapping Rain Water/Approach 1/solution.py

@@ -0,0 +1,21 @@
+class Solution:
+    def trap(self, height: List[int]) -> int:
+        if not height:
+            return 0
+        n = len(height)
+        lm = [0] * n
+        rm = [0] * n
+
+        lm[0] = height[0]
+        for i in range(1, n):
+            lm[i] = max(lm[i - 1], height[i])
+
+        rm[n - 1] = height[n - 1]
+        for i in range(n - 2, -1, -1):
+            rm[i] = max(rm[i + 1], height[i])
+
+        water = 0
+        for i in range(n):
+            water += min(lm[i], rm[i]) - height[i]
+
+        return water