Submission #878042

#	Time	Username	Problem	Language	Result	Execution time	Memory
878042		kh0i	Joker (BOI20_joker)	C++17	49 / 100	1910 ms	30500 KiB

Joker

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

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...)
#endif

using ll = long long;
using pii = pair<int, int>;

#define F first
#define S second
#define sz(x) (int)((x).size())
#define all(x) (x).begin(), (x).end()

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll get_rand(ll l, ll r) {
    assert(l <= r);
    return uniform_int_distribution<ll> (l, r)(rng);
}

const int N = 2e5 + 3;

int n, m, q, L[N], R[N];
vector<pii> g[N];
pii e[N];

// contain no odd cycle -> bipartite graph

namespace Sub12{
    bool valid_input(){
        return n <= 2000 and m <= 2000 and q <= 2000;
    }

    int vis[N];

    bool dfs(int u, int l, int r, int col){
        bool ok = 1;
        vis[u] = col;
        for(auto [v, id] : g[u]){
            if(l <= id and id <= r)
                continue;
            if(vis[v])
                ok &= (vis[u] != vis[v]);
            else
                ok &= dfs(v, l, r, col ^ 3);
        }
        return ok;
    }

    void solve(){
        for(int i = 1; i <= q; ++i){
            bool bipartite = 1;
            for(int u = 1; u <= n; ++u)
                vis[u] = 0;
            for(int u = 1; u <= n; ++u){
                if(!vis[u])
                    bipartite &= dfs(u, L[i], R[i], 1);
            }
            cout << (bipartite ? "NO\n" : "YES\n");
        }
    }
}

struct DSU{
    bool bipartite = 1;
    vector<pii> p;
    int n;

    void init(int _n){
        n = _n;
        p.resize(n + 2);
        for(int i = 1; i <= n; ++i)
            p[i] = {i, 0};
    }

    pii find_set(int u){
        if(u != p[u].F){
            int parity = p[u].S;
            p[u] = find_set(p[u].F);
            p[u].S ^= parity;
        }
        return p[u];
    }

    void add_edge(int u, int v){
        pii pu = find_set(u);
        u = pu.F;
        pii pv = find_set(v);
        v = pv.F;
        int x = pu.S, y = pv.S;
        if(u == v){
            bipartite &= (x != y);
            return;
        }
        p[v] = {u, x ^ y ^ 1};
    }
};

namespace Sub34{
    bool valid_input(){
        bool ok = 1;
        for(int i = 1; i <= q; ++i)
            ok &= (L[i] <= 200);
        return ok;
    }

    int ans[N];
    vector<pii> d[N];

    void solve(){
        for(int i = 1; i <= q; ++i){
            d[L[i]].push_back({R[i], i});
        }
        for(int i = 1; i <= min(200, m); ++i){
            DSU dsu;
            dsu.init(n);
            for(int j = 1; j < i; ++j){
                dsu.add_edge(e[j].F, e[j].S);
            }
            sort(all(d[i]), [](pii &x, pii &y) -> bool{
                 return x.F < y.F;
            });

            for(int j = m; j >= i; --j){
                while(!d[i].empty() and d[i].back().F == j){
                    ans[d[i].back().S] = dsu.bipartite;
                    d[i].pop_back();
                }
                dsu.add_edge(e[j].F, e[j].S);
            }
        }
        for(int i = 1; i <= q; ++i)
            cout << (ans[i] ? "NO\n" : "YES\n");
    }
}

void solve(){
    cin >> n >> m >> q;
    for(int i = 1; i <= m; ++i){
        int u, v;
        cin >> u >> v;
        g[u].push_back({v, i});
        g[v].push_back({u, i});
        e[i] = {u, v};
    }
    for(int i = 1; i <= q; ++i)
        cin >> L[i] >> R[i];
    if(Sub12::valid_input())
        Sub12::solve();
    else if(Sub34::valid_input())
        Sub34::solve();
}

int32_t main() {
    cin.tie(nullptr)->sync_with_stdio(0);
    #define task "nohome"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int test = 1;
//    cin >> test;
    for(int i = 1; i <= test; ++i){
//        cout << "Case #" << i << ": ";
        solve();
    }
    #ifdef LOCAL
        cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
    #endif
    return 0;
}

Compilation message (stderr)

Joker.cpp: In function 'int32_t main()':
Joker.cpp:161:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  161 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Joker.cpp:162:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  162 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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