42. Trapping Rain Water.md

title	toc	date	tags	top
42. Trapping Rain Water	false	2017-10-30	Leetcode greedy algorithm Array Two Pointers Stack	42

Given $n$ non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.

For example, Given [0,1,0,2,1,0,1,3,2,1,2,1], return 6.

The above elevation map 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. Thanks Marcos for contributing this image!