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.
height = [0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1]
Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6 Explanation: The above elevation map traps 6 units of rain water.
height = [4, 2, 0, 3, 2, 5]
Input: height = [4,2,0,3,2,5] Output: 9 Explanation: The elevation map traps 9 units of rain water total.
1 <= height.length <= 2 * 10^40 <= height[i] <= 10^5height = [0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1]