AT1219 歴史の研究

题意

关于回滚莫队见这篇博客。

code:

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=1e5+10;
const int maxt=350;
int n,Q,t,num,block,nowl,nowr;
int a[maxn],b[maxn],L[maxt],R[maxt],pos[maxn],cnt[maxn],tmpcnt[maxn];
ll nowans;
ll ans[maxn];
struct Query{int l,r,id;}qr[maxn];
inline bool cmp(Query x,Query y){return (pos[x.l]==pos[y.l])?(x.r<y.r):(pos[x.l]<pos[y.l]);}
inline void erase(int x){cnt[a[x]]--;}
inline void add(int x)
{
	cnt[a[x]]++;
	nowans=max(nowans,1ll*cnt[a[x]]*b[a[x]]);
}
int main()
{
	scanf("%d%d",&n,&Q);
	for(int i=1;i<=n;i++)scanf("%d",&a[i]),b[i]=a[i];
	sort(b+1,b+n+1);num=unique(b+1,b+n+1)-(b+1);
	for(int i=1;i<=n;i++)a[i]=lower_bound(b+1,b+num+1,a[i])-b;
	t=sqrt(n);block=n/t;
	if(n%t)block++;
	for(int i=1;i<=block;i++)L[i]=(i-1)*t+1,R[i]=min(i*t,n);
	for(int i=1;i<=n;i++)pos[i]=(i-1)/t+1;
	for(int i=1;i<=Q;i++)scanf("%d%d",&qr[i].l,&qr[i].r),qr[i].id=i;
	sort(qr+1,qr+Q+1,cmp);
	int last=0;nowl=1,nowr=0;
	for(int i=1;i<=Q;i++)
	{
		if(pos[qr[i].l]==pos[qr[i].r])
		{
			ll res=0;
			for(int j=qr[i].l;j<=qr[i].r;j++)tmpcnt[a[j]]++;
			for(int j=qr[i].l;j<=qr[i].r;j++)res=max(res,1ll*tmpcnt[a[j]]*b[a[j]]);
			for(int j=qr[i].l;j<=qr[i].r;j++)tmpcnt[a[j]]--;
			ans[qr[i].id]=res;
			continue;
		}
		if(pos[qr[i].l]!=last)
		{
			while(nowr>R[pos[qr[i].l]])erase(nowr--);
			while(nowl<R[pos[qr[i].l]]+1)erase(nowl++);
			nowans=0;last=pos[qr[i].l];
		}
		while(nowr<qr[i].r)add(++nowr);
		ll tmp=nowans;int tmpl=nowl;
		while(nowl>qr[i].l)add(--nowl);
		ans[qr[i].id]=nowans;
		while(nowl<tmpl)erase(nowl++);
		nowans=tmp;
	}
	for(int i=1;i<=Q;i++)printf("%lld
",ans[i]);
	return 0;
}