Submission #856007

#	Time	Username	Problem	Language	Result	Execution time	Memory
856007		Pannda	Abracadabra (CEOI22_abracadabra)	C++17	100 / 100	527 ms	48224 KiB

Main

#include <bits/stdc++.h>
using namespace std;

const int LOG = 20;

struct Fenwick {
    int n;
    vector<int> bit;
    vector<int> a;
    Fenwick(int n) : n(n), bit(n + 1, 0), a(n, 0) {}

    void add(int i, int delta) {
        a[i] += delta;
        for (i++; i <= n; i += i & -i) {
            bit[i] += delta;
        }
    }

    int sum(int i) {
        int res = 0;
        for (; i > 0; i -= i & -i) {
            res += bit[i];
        }
        return res;
    }

    int get(int i) {
        return a[i];
    }

    int kth(int k) {
        int sum = 0;
        int cur = 0;
        for (int i = LOG - 1; i >= 0; i--) {
            if (cur + (1 << i) <= n && sum + bit[cur + (1 << i)] <= k) {
                cur += (1 << i);
                sum += bit[cur];
            }
        }
        return cur;
    }
};

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

    int n, q;
    cin >> n >> q;
    vector<int> a(n), ia(n);
    vector<vector<array<int, 2>>> mp(n + 1);
    vector<int> ans(q);

    for (int i = 0; i < n; i++) {
        cin >> a[i];
        a[i]--;
        ia[a[i]] = i;
    }

    for (int id = 0; id < q; id++) {
        int t, i;
        cin >> t >> i;
        i--;
        t = min(t, n);
        mp[t].push_back({ i, id });
    }

    vector<int> dec;
    vector<int> f(n);
    for (int i = n - 1; i >= 0; i--) {
        while (!dec.empty() && a[i] > a[dec.back()]) {
            dec.pop_back();
        }
        f[i] = dec.empty() ? n : dec.back();
        dec.push_back(i);
    }

    Fenwick fen(n);
    for (int i = 0; i < n; i = f[i]) {
        fen.add(a[i], f[i] - i);
    }

    function<void()> cut = [&]() {
        int head = fen.kth(n / 2);
        int pos = fen.sum(head);
        int fromLen = fen.get(head);
        int toLen = n / 2 - pos;
        fen.add(head, -fromLen + toLen);

        int newHead = a[ia[head] + toLen];
        int i = ia[newHead];
        int k = n / 2;
        int bound = pos + fromLen;
        while (k + f[i] - i < bound) {
            fen.add(a[i], f[i] - i);
            k += f[i] - i;
            i = f[i];
        }
        fen.add(a[i], bound - k);
    };

    function<int(int)> kth = [&](int k) {
        int head = fen.kth(k);
        int pos = fen.sum(head);
        int delta = k - pos;
        return a[ia[head] + delta];
    };

    for (int t = 0; t <= n; t++) {
        for (auto [i, id] : mp[t]) {
            ans[id] = kth(i);
        }
        cut();
    }

    for (auto x : ans) {
        cout << x + 1 << '\n';
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 40 / 40
• Subtask 3: 25 / 25
• Subtask 4: 25 / 25