[LintCode] Trapping Rain Water 收集雨水

Posted 2020-08-23 Grandyang

 

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.

Have you met this question in a real interview? 

Yes

Example

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

Challenge 

O(n) time and O(1) memory

O(n) time and O(n) memory is also acceptable.

 

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