题解 | #接雨水问题#

#define ll long long
class Solution {
public:
    ll maxWater(vector<int>& arr) {
        ll res=0;
        int l=0,r=arr.size()-1;
        while(l<r)
        {
            if(arr[l]<arr[r])
            {
                int k=arr[l];
                while(l<r&&arr[l]<=k)res+=k-arr[l],l++;
            }
            else {
                int k=arr[r];
                while(l<r&&arr[r]<=k)res+=k-arr[r],r--;
            }
        }
        return res;
    }
};