Leetcode 42. Trapping Rain Water
Given an array of non-negative heights representing elevation bars of width 1, compute the total units of water that can be trapped between them after raining. The core challenge is determining, for each position, the bounding left and right maxima to accumulate trapped volume efficiently (ideally in linear time).
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Early September, 2026
Late August, 2026
Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining. Example 1: Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6 Explanation: The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Example 2: Input: height = [4,2,0,3,2,5] Output: 9
Early August, 2026
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