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Modified once the monotony of the queue, the queue is determined by means of monotonous reach the maximum interval delete, and then by means of a continuous growth of l, r to solve, very good question
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#include<bits/stdc++.h> using namespace std; long long a[2000005],n,p,d,sum[2000005],q[2000005],last=1,hd,tl,t[2000005],ans; int main() { cin>>n>>p>>d; for(int i=1;i<=n;i++){cin>>a[i];sum[i]=sum[i-1]+a[i];} for(int i=d;i<=n;i++)t[i]=sum[i]-sum[i-d]; ans=d;q[++tl]=d; for(int i=d+1;i<=n;i++) { while(hd<=tl&&t[q[tl]]<t[i])tl--; q[++tl]=i; while(hd<=tl&&q[hd]-d+1<last)hd++; while(hd<=tl&&sum[i]-sum[last-1]-t[q[hd]]>p) { last++; while(hd<=tl&&q[hd]-d+1<last)hd++; } ans=max(i-last+1,ans); } cout<<ans; }