接雨水

题目链接：https://leetcode-cn.com/problems/trapping-rain-water/
题目描述：

题解：

class Solution {
public:
    int trap(vector<int>& height) {
        vector<int> maxLeft(height.size(), 0);
        vector<int> maxRight(height.size(), 0);

        //记录每个柱子左边的最大高度
        maxLeft[0] = height[0];
        for(int i = 1; i < height.size(); i++)
        {
            maxLeft[i] = max(height[i], maxLeft[i - 1]);
        }
        //记录每个柱子右边的最大高度
        maxRight[height.size() - 1] = height[height.size() - 1];
        for(int i = height.size() - 2; i >= 0; i--)
        {
            maxRight[i] = max(height[i], maxRight[i + 1]);
        }
        int sum = 0;
        for(int i = 0; i < height.size(); i++)
        {
            int count = min(maxLeft[i], maxRight[i]) - height[i];
            if(count > 0)
                sum += count;
        }
        return sum;
    }
};