4385: [POI2015]Wilcze doły|单调队列

单调队列的题怎么总感觉不是很好想..
枚举右区间，维护一个长度为d的区间使其区间和单调递减并且顺序是从左到右

#include<algorithm>#include<iostream>#include<cstdlib>#include<cstring>#include<vector>#include<cstdio>#include<queue>#include<cmath>#include<set>#include<map>#define ll long long#define N 2000005using namespace std;ll sc(){    ll i=0; char c=getchar();    while(c>'9'||c<'0')c=getchar();    while(c>='0'&&c<='9')i=i*10+c-'0',c=getchar();    return i;} ll a[N],p;int n,d,q[N],ans;int main(){    n=sc(),p=sc(),d=sc();    for(int i=1;i<=n;i++)a[i]=a[i-1]+sc();    int l=1,r=0,st=0;ans=d;    for(int i=d;i<=n;i++)    {        while(l<=r&&a[q[r]]-a[q[r]-d]<a[i]-a[i-d])r--;        q[++r]=i;        while(a[i]-a[st]-a[q[l]]+a[q[l]-d]>p)        {            st++;            if(q[l]-d<st)l++;        }        //cout << i<<" "<< st<< endl;        ans=max(ans,i-st);    }    cout<<ans;    return 0;}