42.接雨水.cpp

/*
 * @lc app=leetcode.cn id=42 lang=cpp
 *
 * [42] 接雨水
 */

// @lc code=start
class Solution {
public:
    int trap(vector<int>& height)
    {
        int left = 0, right = height.size() - 1;
        int ans = 0;
        int left_max = 0, right_max = 0;
        while (left < right) {
            if (height[left] < height[right]) {
                height[left] >= left_max ? (left_max = height[left]) : ans += (left_max - height[left]);
                ++left;
            }
            else {
                height[right] >= right_max ? (right_max = height[right]) : ans += (right_max - height[right]);
                --right;
            }
        }
        return ans;
    }
};
// @lc code=end