Trapped Rain water problem in python

Python/TrappedRainWaterProblem.py

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+def trapping_water_problem(heights):
+    if len(heights) < 3:
+        return 0
+
+    left_max = [0 for _ in range(len(heights))]
+    right_max = [0 for _ in range(len(heights))]
+
+    # dealing with the left max values
+    for i in range(1, len(heights)):
+        left_max[i] = max(left_max[i - 1], heights[i - 1])
+
+    # dealing with the right max values
+    for i in range(len(heights) - 2, -1, -1):
+        right_max[i] = max(right_max[i + 1], heights[i + 1])
+
+    # consider all the items in O(N) and sum up the trapped rain water units
+    trapped = 0
+
+    for i in range(1, len(heights) - 1):
+        if min(left_max[i], right_max[i]) > heights[i]:
+            trapped += min(left_max[i], right_max[i]) - heights[i]
+
+    return trapped
+
+
+if __name__ == '__main__':
+    print(trapping_water_problem([1, 0, 2, 1, 3, 1, 2, 0, 3]))