Submission #973447

#	Time	Username	Problem	Language	Result	Execution time	Memory
973447		cot7302	Joker (BOI20_joker)	C++17	0 / 100	1 ms	2396 KiB

Joker

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

struct disjoint_set {
    int n, odd_cir;
    vector<int> _, odd_cir_op;
    vector<tuple<int, int, int>> op;
    disjoint_set(int n) : n(n), odd_cir(0), _(2 * n + 1, -1), odd_cir_op(), op() {}

    int root(int x) { while (_[x] > 0) x = _[x]; return x; }

    void __join(int a, int b) {
        a = root(a), b = root(b);
        if (a == b) return;
        if (_[a] > _[b]) swap(a, b);
        op.emplace_back(a, b, _[b]);
        _[a] += _[b];
        _[b] = a;
    }

    void join(int a, int b) {
        __join(a, b + n);
        __join(a + n, b);
        odd_cir += odd_cir_op.emplace_back(root(a) == root(b));
    }

    void join(pair<int, int> x) {
        auto [a, b] = x;
        join(a, b);
    }

    bool is_bipartite() const {
        return odd_cir;
    }

    void roll_back(int cnta, int cntb) {
        while (cnta != (int)size(op)) {
            auto [a, b, sz] = op.back();
            _[a] -= sz;
            _[b] = sz;
            op.pop_back();
        }
        while (cntb != (int)size(odd_cir_op)) {
            odd_cir -= odd_cir_op.back();
            odd_cir_op.pop_back();
        }
    }

    void roll_back(pair<int, int> x) {
        roll_back(x.first, x.second);
    }

    pair<int, int> snapshot() const {
        return {(int)size(op), (int)size(odd_cir_op)};
    }
};

pair<int, int> edges[200001];

int ans[200001];

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m, q; cin >> n >> m >> q;
    for (int i = 1; i <= m; i++) cin >> edges[i].first >> edges[i].second;
    disjoint_set dsu(n);
    for (int i = 1; i <= m; i++) dsu.join(edges[i]);
    if (dsu.is_bipartite()) {
        while (q--) cout << "NO\n";
        return 0;
    }
    dsu.roll_back(0, 0);
    auto solve = [&](auto&& f, int l, int r, int ql, int qr) -> void {
        if (l > r) return;
        int mid = (l + r) >> 1;
        auto snap = dsu.snapshot();
        for (int i = l; i < mid; i++) dsu.join(edges[i]);
        int opt = qr;
        while (dsu.is_bipartite()) dsu.join(edges[opt--]);
        ans[mid] = opt;
        dsu.roll_back(snap);
        snap = dsu.snapshot();
        for (int i = opt + 1; i <= qr; i++) dsu.join(edges[i]);
        f(f, l, mid - 1, ql, opt);
        dsu.roll_back(snap);
        snap = dsu.snapshot();
        for (int i = l; i <= mid; i++) dsu.join(edges[i]);
        f(f, mid + 1, r, opt, qr);
        dsu.roll_back(snap);
    };

    solve(solve, 1, m, 0, m);
    //for (int i = 0; i < m; i++) cout << ans[i] << " \n"[i == m - 1];
    for (int l, r; q--; ) {
        cin >> l >> r;
        cout << ((r <= ans[l]) ? "YES\n" : "NO\n");
    }
}

• Subtask 1: 0 / 6
• Subtask 2: 0 / 8
• Subtask 3: 0 / 25
• Subtask 4: 0 / 10
• Subtask 5: 0 / 22
• Subtask 6: 0 / 29