Submission #389069

#	Time	Username	Problem	Language	Result	Execution time	Memory
389069		arujbansal	Joker (BOI20_joker)	C++17	0 / 100	242 ms	10620 KiB

Joker

#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <array>
#include <stack>
#include <queue>
#include <random>
#include <numeric>
#include <functional>
#include <chrono>
#include <utility>
#include <iomanip>
#include <assert.h>

using namespace std;

void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail>
void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)

#define rng_init mt19937 rng(chrono::steady_clock::now().time_since_epoch().count())
#define rng_seed(x) mt19937 rng(x)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()
// #define int long long

const int MXN = 2e5 + 5, INF = 1e9 + 5;
int N, M, Q;
pair<int, int> edges[MXN];
int info[MXN], parity[MXN];
int is_bipartite;
stack<array<int, 3>> changes; // {node, size of component, did this make the graph non bipartite}
int valid[MXN];

int find_par(int x) {
    if (info[x] < 0) return x;

    int p = find_par(info[x]);
    parity[x] ^= parity[info[x]];
    
    return p;
}

void unite(int x, int y) {
    int px = find_par(x), py = find_par(y);

    if (px == py) {
        if (parity[x] == parity[y]) {
            changes.emplace(array<int, 3>{py, -info[py], is_bipartite});
            is_bipartite = 0;
        }

        return;
    }
    
    if (info[px] > info[py]) {
        swap(px, py);
        swap(x, y);
    }

    changes.emplace(array<int, 3>{py, -info[py], 0});

    parity[py] = parity[x] ^ parity[y] ^ 1;
    info[px] += info[py];
    info[py] = px;
}   

void rollback() {
    assert(changes.empty() == false);

    auto [y, comp_sz, non_bipartite] = changes.top();

    int x = info[y];
    if (x == y) return;

    info[x] += comp_sz;
    info[y] = -comp_sz;

    if (non_bipartite)
        is_bipartite = 1;

    changes.pop();
}

void dnc(int l, int r, int optl, int optr) {
    if (l > r) return;

    // dbg(l, r);

    int mid = (l + r) / 2, ufds_r = optr;

    while (ufds_r > mid + 1 && ufds_r > optl && is_bipartite) {
        ufds_r--;
        unite(edges[ufds_r].first, edges[ufds_r].second);
    }

    valid[mid] = (is_bipartite ? 0 : ufds_r);

    int midl = (l + mid - 1) / 2, midr = (mid + 1 + r) / 2, best = ufds_r;

    while (ufds_r < optr) {
        rollback();
        ufds_r++;
    }

    for (int i = mid; i < midr; i++)
        unite(edges[i].first, edges[i].second);

    dnc(mid + 1, r, best, optr);

    for (int i = mid; i < midr; i++)
        rollback();

    for (int i = mid - 1; i >= midl; i--)
        rollback();

    for (int i = ufds_r - 1; i >= best; i--)
        unite(edges[i].first, edges[i].second);

    dnc(l, mid - 1, optl, ufds_r);

    for (int i = midl; i < mid; i++)
        unite(edges[i].first, edges[i].second);
}

void solve() {
    cin >> N >> M >> Q;

    for (int i = 0; i < M; i++) {
        cin >> edges[i].first >> edges[i].second;
        edges[i].first--, edges[i].second--;
    }

    is_bipartite = 1;
    for (int i = 0; i < MXN; i++)
        info[i] = -1, parity[i] = 0;

    for (int i = 0; i < M / 2; i++)
        unite(edges[i].first, edges[i].second);

    dnc(0, M - 1, 0, M);

    while (Q--) {
        int l, r;
        cin >> l >> r;
        l--, r--;

        cout << (valid[l] > r ? "YES" : "NO") << "\n";
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int TC = 1;
    // cin >> TC;
    while (TC--) solve();
}

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