bzoj1878: [SDOI2009]HH的项链

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define rep(i,s,t) for(int i=s;i<=t;i++)
#define dwn(i,s,t) for(int i=s;i>=t;i--)
#define clr(x,c)  memset(x,c,sizeof(x))
int read(){
    int x=0;char c=getchar();
    while(!isdigit(c)) c=getchar();
    while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();
    return x;
} 
const int nmax=50005;
const int maxn=1000005;
int sum[nmax],pos[maxn],next[nmax],a[nmax],n;
struct node{
    int s,t,id,ans;
};
node ns[nmax<<2];
bool cmp(node a,node b){
    return a.s<b.s||a.s==b.s&&a.t<b.t;
}
bool comp(node a,node b){
    return a.id<b.id;
}
void update(int x){
    for(int i=x;i<=n;i+=i&-i) sum[i]+=1;
}
int query(int x){
    int ans=0;
    for(int i=x;i;i-=i&-i) ans+=sum[i];
    return ans;
}
void maxs(int &a,int b){
    if(a<b) a=b;
}
int main(){
    n=read();int mx=-1;
    rep(i,1,n) a[i]=read(),maxs(mx,a[i]);
    dwn(i,n,1) next[i]=pos[a[i]],pos[a[i]]=i;
    rep(i,0,mx) if(pos[i]) update(pos[i]);
     
    int m=read();
    rep(i,1,m) ns[i].s=read(),ns[i].t=read(),ns[i].id=i;
    sort(ns+1,ns+m+1,cmp);
    int cur=1;
    rep(i,1,m){
        rep(j,cur,ns[i].s-1) if(next[j]) update(next[j]);
        cur=ns[i].s;
        ns[ns[i].id].ans=query(ns[i].t)-query(ns[i].s-1);
    }
    rep(i,1,m) printf("%d\n",ns[i].ans);
    return 0;
}