Mo.cpp

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
uniform_int_distribution<int> dist(1, 10);
#define ll long long
#define ld long double
#define gcd(a, b) __gcd(a, b)
#define lcm(a,b) a/gcd(a,b)*b
#define pb push_back
#define ii pair<int,int>
#define vi vector<int>
#define vii vector<pair<int,int>>
#define F first
#define S second
#define sz(x) (int)x.size()
#define fast ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fore(a, b, c) for(int a=b; a<c; ++a)
#define all(x) x.begin(), x.end()
#define int ll
#define endl '\n';
template <typename T>
using ordered_set = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>;
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#define dbg(x...) cerr << "[" << #x << "] = ["; _print(x)
#define raya cerr << "==========================" << endl;
const double EPS = 1e-7;
const double PI = acos(-1);
const int MOD = 1e9+7;  
int TC = 0;

// Problem: D-Query (SPOJ)

int block_size;

struct Query {
    int l, r, idx;

    bool operator<(const Query &o) const {
        if (l / block_size != o.l / block_size) {
            // si son de bloques distintos
            return tie(l, r) < tie(o.l, o.r);
        }
        // son del mismo bloque
        return ((l / block_size) & 1) ? (r < o.r) : (r > o.r);   // es una optimizacion
    }

};

const int X = 1e6+5;
int freq[X];

void solve(){
    int n;
    cin >> n;
    vi a(n);
    fore(i, 0, n){
        cin >> a[i];
    }

    int q;
    cin >> q;
    vector<Query> queries(q);
    fore(i, 0, q){
        cin >> queries[i].l >> queries[i].r;
        queries[i].l--, queries[i].r--;
        queries[i].idx = i;
    }


    // Mo
    block_size = sqrt((int)ceil(n));
    sort(all(queries));
    vector<int> ans(q);
    int cur_l = -1;
    int cur_r = -1;

    // depende del problema (d-query)
    int cnt = 0;

    auto add = [&](int i) -> void {
        if (++freq[a[i]] == 1) {
            cnt++;
        }
    };

    auto remove = [&](int i) -> void {
        if (--freq[a[i]] == 0) {
            cnt--;
        }
    };

    for (Query q : queries) {
        while (cur_l > q.l) {
            cur_l--;
            add(cur_l);
        }
        while (cur_r < q.r) {
            cur_r++;
            add(cur_r);
        }
        while (cur_l < q.l) {
            remove(cur_l);
            cur_l++;
        }
        while (cur_r > q.r) {
            remove(cur_r);
            cur_r--;
        }
        ans[q.idx] = cnt;
    }

    fore (i, 0, q) {
        cout << ans[i] << endl;
    }

}
    
signed main(){
    fast;
    int tt = 1;
    // cin >> tt;
    while(tt--){
        TC++;
        solve();
    }
}