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  • 「题解」洛谷 SP3267 DQUERY

    题目

    SP3267 DQUERY - D-query

    思路

    莫队板子,统计数字出现次数。

    Code

    #include <cmath>
    #include <cstdio>
    #include <cstring>
    #include <string>
    #include <iostream>
    #include <algorithm>
    #define M 1000001
    
    int n, m, a[M], ans[M];
    int sqrn, num[M], cnt[M];
    struct query {
        int x, y, id;
        friend bool operator < (query q1, query q2) {
            if (num[q1.x] == num[q2.x]) return q1.y < q2.y;
            return num[q1.x] < num[q2.x];
        }
    }q[M];
    
    void add(int x, int &now) {
        ++cnt[x];
        if (cnt[x] == 1) ++now;
    }
    
    void del(int x, int &now) {
        --cnt[x];
        if (cnt[x] == 0) --now;
    }
    
    int main() {
        scanf("%d", &n);
        for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
        scanf("%d", &m), sqrn = n / sqrt(m);
        for (int i = 1; i <= n; ++i) num[i] = (i - 1) / sqrn + 1;
        for (int i = 1; i <= m; ++i) {
            scanf("%d %d", &q[i].x, &q[i].y);
            q[i].id = i;
        }
        std::sort(q + 1, q + m + 1);
        int l = 1, r = 1, now = 1;
        cnt[a[1]] = 1;
        for (int i = 1; i <= m; ++i) {
            while (l > q[i].x) add(a[--l], now);
            while (r < q[i].y) add(a[++r], now);
            while (l < q[i].x) del(a[l++], now);
            while (r > q[i].y) del(a[r--], now);
            ans[q[i].id] = now;
        }
        for (int i = 1; i <= m; ++i) printf("%d
    ", ans[i]);
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/poi-bolg-poi/p/13902045.html
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