7/13 训练笔记

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回滚莫队板题被卡到 28pts 了

歴史の研究

回滚莫队题。莫队笔记

考虑很好加（维护 cnt 并更新答案即可），但是不好删。
那么回滚莫队
代码：

#include <bits/stdc++.h>
#define int long long
#define rep(i, l, r) for (int i = l; i <= r; i++)
#define per(i, l, r) for (int i = l; i >= r; i--)
using namespace std;
int a[100010], bel[100010], ed[100010], ans[100010], n, q1, B, res;
unordered_map<int, int> cnt, cnt1;
int id(int i) { return bel[i]; }
struct query {
    int l, r, id1;
    query(int l = 0, int r = 0, int id1 = 0):l(l), r(r), id1(id1) {}
    bool operator<(query o) {
        return (id(l) != id(o.l)) ? id(l) < id(o.l) : r < o.r;
    }
    query operator=(query o) {
        l = o.l;
        r = o.r;
        id1 = o.id1;
        return *this;
    }
}q[200010];
void add(int x) {
    cnt[x]++;
    res = max(res, cnt[x] * x);
}
int bruteForce(int l, int r) {
    cnt1.clear();
    int res = 0;
    rep (i, l, r) {
        cnt1[a[i]]++;
        res = max(res, a[i] * cnt1[a[i]]);
    }
    return res;
}
signed main() {
    cin >> n >> q1;
    B = sqrt(n);
    rep (i, 1, n) {
        cin >> a[i];
        bel[i] = (i - 1) / B + 1;
        ed[bel[i]] = i;
    }
    rep (i, 1, q1) {
        cin >> q[i].l >> q[i].r;
        q[i].id1 = i;
    }
    sort(q + 1, q + q1 + 1);
    // rep (i, 1, q1) {
    //     cout << q[i].l << " " << q[i].r << " " << id(q[i].l) << "\n";
    // }
    int l = 0, r = -1;
    rep (i, 1, q1) {
        if (id(l) != id(q[i].l)) {
            l = ed[id(q[i].l)];
            r = l - 1;
            res = 0;
            cnt.clear();
        }
        if (id(q[i].r) != id(l)) {
            // if (q[i].l == 2 && q[i].r == 5) {
            //     cout << l << " " << r << "\n";
            // }
            // if (q[i].l == 1 && q[i].r == 7) {
            //     rep (i, 1, n) {
            //         cout << "[ " << a[i] << " " << cnt[a[i]] << " ]" << "\n";
            //     }
            //     cout << l << " " << r << " " << bel[q[i].l] << " " << ed[q[i].l] << " " << res << "\n";
            // }
            while (r < q[i].r) add(a[++r]);
            // if (q[i].l == 1 && q[i].r == 4) {
            //     rep (i, 1, n) {
            //         cout << a[i] << " " << cnt[a[i]] << "\n";
            //     }
            //     cout << res << "\n";
            // }
            int t = res;
            while (l > q[i].l) add(a[--l]);
            // if (q[i].l == 3 && q[i].r == 6) {
            //     rep (i, 1, n) {
            //         cout << a[i] << " " << cnt[a[i]] << "\n";
            //     }
            //     cout << t << " " << res << "\n";
            // }
            // if (q[i].l == 1 && q[i].r == 4) {
            //     cout << t << "\n";
            // }
            ans[q[i].id1] = res;
            res = t;
            l = ed[id(l)];
            rep (j, q[i].l, l - 1) {
                cnt[a[j]]--;
            }
        } else {
            ans[q[i].id1] = bruteForce(q[i].l, q[i].r);
        }
    }
    rep (i, 1, q1) {
        cout << ans[i] << "\n";
    }
}