Problem: 42. 接雨水

思路

很多解法

解题方法

只需分别计算每个格子能承接的雨水即可，每个格子能接的雨水取决于它左右两侧最高的格子，再使用双指针遍历，即可。

Code

class Solution {
public:
    int trap(vector<int>& height) {
        int n = height.size();
        int l = 0;
        int r = n - 1;

        int ans = 0;
        int lmax = height[l];
        int rmax = height[r];

        while (l < r) {
            lmax = max(lmax, height[l]);
            rmax = max(rmax, height[r]);
            if (lmax < rmax) {
                ans += lmax - height[l];
                l++;
            }
            else {
                ans += rmax - height[r];
                r--;
            }
        }
        return ans;
    }
};

class Solution {
    public int trap(int[] height) {
        int n = height.length;
        int ans = 0;

        int l = 0;
        int r = n-1;

        int left = 0;
        int right = 0;
        while(l < r){
            left = Math.max(left, height[l]);
            right = Math.max(right, height[r]);
            if(height[l] < height[r]){
                ans += left - height[l];
                l++;
            }
            else{
                ans += right - height[r];
                r--;
            }
        }
        return ans;
    }
}