No.48-LeetCode42 - 一维蓄水

贪心思想，从两边往中间扫，高度小的边移动：

class Solution {
public:
    int trap(vector<int>& height) {
        int N = height.size();
        int maxL,maxR;
        int L,R;
        L = maxL = maxR = 0;
        R = N-1;
        int ans = 0;
        while(L<R){
            maxL = max(maxL,height[L]);
            maxR = max(maxR,height[R]);
            if(maxL < maxR){
                ans += max(0,maxL - height[L]);
                L++;
            }else{
                ans += max(0,maxR - height[R]);
                R--;
            }
        }
        return ans;
    }
};