luogu P1725 琪露诺 单调队列dp

#include<map>
#include<queue>
#include<time.h>
#include<limits.h>
#include<cmath>
#include<ostream>
#include<iterator>
#include<set>
#include<stack>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define rep_1(i,m,n) for(int i=m;i<=n;i++)
#define mem(st) memset(st,0,sizeof st)
int read()
{
    int res=0,ch,flag=0;
    if((ch=getchar())=='-')             //判断正负
        flag=1;
    else if(ch>='0'&&ch<='9')           //得到完整的数
        res=ch-'0';
    while((ch=getchar())>='0'&&ch<='9')
        res=res*10+ch-'0';
    return flag?-res:res;
}
typedef long long ll;
typedef pair<int,int> pii;
typedef unsigned long long ull;
typedef pair<double,double> pdd;
const int inf = 0x3f3f3f3f;
const int N=2e6+10;
int a[N];
int f[N];
int q[N];
void solve()
{
    int n,l,r;
    cin>>n>>l>>r;
    for(int i=0; i<=n; i++)
        cin>>a[i];
    int hh=1,tt=1;
    memset(f,0xcf,sizeof(f));f[0]=0;
    int ans=-0x3f3f3f3f;
    for(int i=l; i<=n; i++)
    {
        while(hh<tt&&q[hh]+r<i)
            hh++;
        while(hh<tt&&f[q[tt-1]]<=f[i-l])
            tt--;
        q[tt++]=i-l;
        f[i]=f[q[hh]]+a[i];
        if(i+r>n)
            ans=max(ans,f[i]);
    }
    cout<<ans<<endl;
}
int main()
{
    int t=1;
    while(t--)
        solve();
    return 0;
}