莫队模版

#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <map>
#include <stack>
#include <set>
#include <queue>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <ctime>
#include <bitset>
#include <cmath>
#include <sstream>
#include <iostream>
#include <unordered_map>

#define ll long long
#define ull unsigned long long
#define ls nod<<1
#define rs (nod<<1)+1
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define INF 0x3f3f3f3f
#define max(a, b) (a>b?a:b)
#define min(a, b) (a<b?a:b)


const double eps = 1e-8;
const int maxn = 1e6 + 10;
const ll MOD = 1e9 + 7;
const int mlog=20;

int sgn(double a) { return a < -eps ? -1 : a < eps ? 0 : 1; }

using namespace std;

struct Req {
    int l,r,id;
}q[maxn];
int n,m,B,Bnum,ans;
int aa[maxn],pos[maxn];
int ANS[maxn],cnt[maxn];

int cmp(Req a, Req b) {
    return (pos[a.l] ^ pos[b.l]) ? pos[a.l] < pos[b.l] : ((pos[a.l] & 1) ? a.r < b.r : a.r > b.r);
}

void upd(int id,int f) {
    cnt[aa[id]] += f;
    if (f == 1 && cnt[aa[id]] == 1)
        ++ans;
    if (f == -1 && cnt[aa[id]] == 0)
        --ans;
}


int main() {
    scanf("%d", &n);
    B = sqrt(n);
    Bnum = ceil((double) n / B);
    for (int i = 1; i <= Bnum; ++i) {
        for (int j = (i - 1) * B + 1; j <= i * B; ++j) {
            pos[j] = i;
        }
    }
    for (int i = 1;i <= n;i++)
        scanf("%d",&aa[i]);
    scanf("%d",&m);
    for(int i = 1; i <= m; ++i) {
        scanf("%d%d",&q[i].l,&q[i].r);
        q[i].id = i;
    }
    sort(q+1,q+1+m,cmp);
    int l = 1,r = 0;
    for (int i = 1;i <= m;i++) {
        while(r<q[i].r) upd(++r, +1);
        while(r>q[i].r) upd(r--, -1);
        while(l<q[i].l) upd(l++, -1);
        while(l>q[i].l) upd(--l, +1);
        ANS[q[i].id] = ans;
    }
    for (int i = 1;i <= m;i++)
        printf("%d\n",ANS[i]);
    return 0;
}