Submission #389105

#	Time	Username	Problem	Language	Result	Execution time	Memory
389105		arujbansal	Joker (BOI20_joker)	C++17	0 / 100	80 ms	14132 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, 4>> changes; // {node, size of component, did this make the graph non bipartite}
int valid[MXN];

pair<int, int> find_par(int x) {
    if (info[x] < 0) return make_pair(x, parity[x]);

    pair<int, int> p = find_par(info[x]);
    p.second ^= 1;
    
    return p;
}

void unite(int x, int y) {
    auto [px, parity_x] = find_par(x);
    auto [py, parity_y] = find_par(y);

    if (px == py) {
        if (parity_x == parity_y) {
            changes.emplace(array<int, 4>{py, -info[py], is_bipartite, parity[py]});
            is_bipartite = 0;
        } else {
            changes.emplace(array<int, 4>{py, -info[py], 0, parity[py]});
        }

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

    changes.emplace(array<int, 4>{py, -info[py], 0, parity[py]});

    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, parity_y] = changes.top();

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

    parity[y] = parity_y;

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

    if (non_bipartite)
        is_bipartite = 1;

    changes.pop();
}

void add_edge(int idx) { unite(edges[idx].first, edges[idx].second); }

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

    int mid = (l + r) / 2;

    // dbg(l, r, mid);
    // dbg(optl, optr);

    // Add prefix of edges
    for (int i = max(0, l - 1); i < mid; i++)
        add_edge(i);

    // dbg(sz(changes));

    int ufds_r = optr; // Edge list pointer

    // Calculate optimal right for mid, store in best
    int best = 0;

    while (ufds_r > mid + 1 && ufds_r >= optl && is_bipartite)
        add_edge(--ufds_r);

    // dbg(ufds_r, sz(changes));

    if (!is_bipartite)
        best = ufds_r;

    valid[mid] = best;

    // dbg(is_bipartite, best);

    // Right side will be dnc(mid + 1, r, best, optr)
    // For right side, already have prefix, need to work on removing suffix
    while (ufds_r < optr) {
        rollback();
        ufds_r++;
    }

    // dbg(ufds_r, sz(changes));
    // dbg(is_bipartite, best);

    // dbg_out();

    // if (mid == 1) {
    //     for (int i = 0; i < N; i++) {
    //         find_par(i);
    //         dbg(i, parity[i]);
    //     }


    //     exit(0);
    // }

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

    // Remove prefix
    for (int i = mid - 1; i >= max(0, l - 1); i--)
        rollback();

    // Now add those edges again
    while (ufds_r > best + 1)
        add_edge(--ufds_r);

    // Left side will be dnc(l, mid - 1, optl, best + 1)
    dnc(l, mid - 1, optl, best + 1);

    // Rollback suffix add
    while (ufds_r < optr) {
        rollback();
        ufds_r++;
    }
}

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;

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

    // for (int i = 0; i < M; i++)
    //     dbg(i, valid[i]);

    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