Trapping Rain Water Between Pillars Problem

amazon Given a list of non-negative integers representing the height of pillars where each pillar has a width of 1. Calculate the amount of rainwater that can be trapped after raining. Example: Input: [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6. Make reasonable assumptions about the data scale. Example Input [0,1,0,2,1,0,1,3,2,1,2,1]