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SP3267 DQUERY - D-query

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题目描述

https://www.luogu.com.cn/problem/SP3267

Solution

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#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#define maxn 30010
#define maxs 1000010
#define maxm 200010
using namespace std;

int n, m, a[maxn]; 

int blo, ans[maxm]; 
struct Query {
    int l, r, id;

    friend bool operator < (const Query &u, const Query &v) {
        if (u.l / blo == v.l / blo) return u.l / blo & 1 ? u.r < v.r : u.r > v.r;
        return u.l < v.l;
    }
} Q[maxm];

int cnt[maxs], Ans;
inline void add(int v) {
    if (++cnt[v] == 1) ++Ans;
}

inline void del(int v) {
    if (--cnt[v] == 0) --Ans;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);

    cin >> n;
    for (int i = 1; i <= n; ++i) cin >> a[i];
    cin >> m; blo = n / sqrt(m); 
    for (int i = 1; i <= m; ++i) cin >> Q[i].l >> Q[i].r, Q[i].id = i; 
    sort(Q + 1, Q + m + 1);
    int l = Q[1].l, r = l - 1;
    for (int i = 1; i <= m; ++i) {
        while (r < Q[i].r) add(a[++r]);
        while (l > Q[i].l) add(a[--l]);
        while (r > Q[i].r) del(a[r--]);
        while (l < Q[i].l) del(a[l++]);
        ans[Q[i].id] = Ans;
    }
    for (int i = 1; i <= m; ++i) cout << ans[i] << "\n"; 
    return 0; 
}