luogu1972 [SDOI2009]HH的项链

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
int n, m, qcnt, ans, col[1000005], bse, blc[50005], a[50005], qwq[200005];
struct Query{
    int xxx, yyy, idx;
}q[200005];
bool cmp(Query u, Query v){
    if(blc[u.xxx]==blc[v.xxx])  return u.yyy<v.yyy;
    else    return blc[u.xxx]<blc[v.xxx];
}
void del(int x){
    if(--col[x]==0) ans--;
}
void add(int x){
    if(++col[x]==1) ans++;
}
void md(){
    int l=1, r=0;
    for(int i=1; i<=m; i++){
        while(l<q[i].xxx)   del(a[l++]);
        while(l>q[i].xxx)   add(a[--l]);
        while(r<q[i].yyy)   add(a[++r]);
        while(r>q[i].yyy)   del(a[r--]);
        qwq[q[i].idx] = ans;
    }
}
int main(){
    cin>>n;
    bse = sqrt(n);
    for(int i=1; i<=n; i++){
        scanf("%d", &a[i]);
        blc[i] = (i - 1) / bse + 1;
    }
    cin>>m;
    for(int i=1; i<=m; i++){
        scanf("%d %d", &q[i].xxx, &q[i].yyy);
        q[i].idx = i;
    }
    sort(q+1, q+1+m, cmp);
    md();
    for(int i=1; i<=m; i++)
        printf("%d\n", qwq[i]);
    return 0;
}