「luogu1972」 [SDOI2009]HH的项链

Posted 2020-10-27 Cupcake

简单莫队

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int N=50010,M=200010,C=1000010;
 4 int n,m,a[N],bel[N],siz,res,cnt[C],ans[M];
 5 struct Q{
 6     int l,r,id;
 7     bool operator<(const Q& k)const{return bel[l]==bel[k.l]?r<k.r:l<k.l;}
 8 }que[M];
 9 inline void expand(int k){
10     if(!cnt[a[k]]) res++;
11     cnt[a[k]]++;
12     return;
13 }
14 inline void reduce(int k){
15     cnt[a[k]]--;
16     if(!cnt[a[k]]) res--;
17     return;
18 }
19 int main(){
20     scanf("%d",&n);
21     siz=pow((double)n,0.5);
22     for(int i=1;i<=n;i++) scanf("%d",&a[i]),bel[i]=(i-1)/siz+1;
23     scanf("%d",&m);
24     for(int i=1;i<=m;i++)scanf("%d%d",&que[i].l,&que[i].r),que[i].id=i;
25     sort(que+1,que+m+1);
26     int nowl=1,nowr=0;
27     for(int i=1;i<=m;i++){
28         while(nowl>que[i].l){nowl--;expand(nowl);}
29         while(nowr<que[i].r){nowr++;expand(nowr);}
30         while(nowl<que[i].l){reduce(nowl);nowl++;}
31         while(nowr>que[i].r){reduce(nowr);nowr--;}
32         ans[que[i].id]=res;
33     }
34     for(int i=1;i<=m;i++) printf("%d\n",ans[i]);
35     return 0;
36 }