Trapping Rain Water

Given an array representing the height of walls, compute how much water can be trapped. Description Given height, a non-negative integer array representing the heights of walls at each unit width. Compute how much water can be trapped after raining. Example Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6 Constraints n == height.length 0 <= n <= 3 * 104 0 <= height[i] <= 105 Note You need to solve the problem in O(n) time complexity. Example Input 0 1 0 2 1 0 1 3 2 1 2 1