本题维护单调栈采用deque

# include <bits/stdc++.h>
using namespace std;
#define int long long
signed main()
{
        int n,m;
        cin>>n>>m;
        vector<int>a(n+1),s(n+1);
        for(int i=1;i<=n;i++)
        cin>>a[i],s[i]=s[i-1]+a[i];
        deque<int>q;
        q.push_back(0);//插入编号0用于更新往后的值防止最大值从一开始的情况
        int res=-1e18;
        for(int i=1;i<=n;i++)
        {
        if(!q.empty()&&i-m>q.front())
        q.pop_front();
        res=max(res,s[i]-s[q.front()]);//序列小于等于m时更新最大值
        while(!q.empty()&&s[i]<s[q.back()]+1)//保证序列严格单调递增
        q.pop_back();
        q.push_back(i);
        }
        cout<<res<<endl;
}