Trapping Rain Water
Given a list of non-negative integers representing elevations of columns, and assuming each column is of equal width of 1, find how much water is trapped in the columns after a rain. Left and right boundaries outside of the columns have 0 elevations.
Input: [3, 2, 1, 2, 2, 3, 2]
Output: 5
Try it yourself
Title
Script
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book.
Contrary to popular belief, Lorem Ipsum is not simply random text.
>>> a = [1, 2, 3]
>>> a[-1]
3