Submission #726706

#	Time	Username	Problem	Language	Result	Execution time	Memory
726706		Johann	Joker (BOI20_joker)	C++14	49 / 100	2053 ms	28660 KiB

Joker

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

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pii> vpii;
typedef vector<vpii> vvpii;
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()

int N, M, Q;
vvpii adj;
vpii E;

struct DSU
{
    vi arr;
    vi color;
    vi cxorp; // xor with color of parent?
    bool oddCycle;
    void init()
    {
        oddCycle = false, arr.resize(N);
        iota(all(arr), 0);
        color.assign(N, 0), cxorp.assign(N, 0);
    }
    int find(int i)
    {
        if (arr[i] == i)
            return i;
        int p = arr[i];
        arr[i] = find(p);
        color[i] = color[p] ^ cxorp[i];
        cxorp[i] = cxorp[i] ^ cxorp[p];
        return arr[i];
    }
    bool join(int a, int b)
    {
        int pa = find(a), pb = find(b); // get color to newest
        bool sameColor = (color[a] == color[b]);
        if (pa == pb)
        {
            oddCycle = oddCycle || sameColor;
            return sameColor;
        }
        arr[pb] = pa;
        if (sameColor)
        {
            cxorp[pb] = 1;
            color[pb] = color[pa] ^ cxorp[pb];
        }
        return false;
    }
};

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> N >> M >> Q;
    adj.resize(N);
    E.resize(M);
    for (int i = 0, a, b; i < M; ++i)
    {
        cin >> a >> b;
        --a, --b;
        adj[a].push_back({b, i}), adj[b].push_back({a, i});
        E[i] = {min(a, b), max(a, b)};
    }

    vvpii Queries(M + 1);
    vi ans(Q);
    for (int i = 0, l, r; i < Q; ++i)
    {
        cin >> l >> r;
        --l, --r; // [l, r] inclusive is blocked
        l = min(M, l), r = min(M, r);
        Queries[l].push_back({r, i});
    }

    DSU dsu;
    for (int l = 0; l < sz(Queries); ++l)
    {
        if (Queries[l].empty())
            continue;
        dsu.init();

        for (int i = 0; i < l; ++i)
            dsu.join(E[i].first, E[i].second);
        int r = M - 1;
        while (!dsu.oddCycle && r >= l)
        {
            dsu.join(E[r].first, E[r].second);
            --r;
        }
        for (pii q : Queries[l])
            ans[q.second] = (q.first <= r);
    }

    for (int a : ans)
        if (a)
            cout << "YES\n";
        else
            cout << "NO\n";

    return 0;
}

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