19.2.4 [LeetCode 42] Trapping Rain Water _leetcode

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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.

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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!
Example:

Input: [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6

题解我觉得这题还挺难的，是我还没有深刻get的思想

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1 class Solution { 2 public: 3int trap(vector< int> & height) { 4int ans = 0, size = height.size(), i = 0; 5stack< int> q; 6while (i < size) { 7if (q.empty()||height[i]< =height[q.top()]) { 8q.push(i++); 9continue; 10} 11else { 12int now = q.top(); q.pop(); 13if (q.empty())continue; 14ans += (min(height[i], height[q.top()]) - height[now])*(i - q.top() - 1); 15} 16} 17return ans; 18} 19 };

View Code【19.2.4 [LeetCode 42] Trapping Rain Water】