251. Trapping Rain Water

Hard · Two Pointers

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.

Examples

Example 1
Input: height = [0,1,0,2,1,0,1,3,2,1,2,1]
Output: 6
Explanation: 6 units of water trapped

Constraints

• 1 ≤ n ≤ 2×10⁴, 0 ≤ heights[i] ≤ 10⁵