Submission #1307365

#	Time	Username	Problem	Language	Result	Execution time	Memory
1307365		pvpro	From Hacks to Snitches (BOI21_watchmen)	C++20	0 / 100	106 ms	24468 KiB

watchmen

#ifndef LOCAL
#pragma GCC Optimize("O3,Ofast,unroll-loops")
#pragma GCC Target("bmi,bmi2,avx,avx2")
#endif
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;

#define int ll

#define f first 
#define s second 
#define mp make_pair 
#define pb push_back
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin() (x).rend()
#ifndef LOCAL
#define endl "\n"
#endif

mt19937 rnd(11);

void solve() {
    int n, m;
    cin >> n >> m;
    vector<vector<int>> graph(n);
    for (int i = 0; i < m; ++i) {
        int a, b;
        cin >> a >> b;
        --a; --b;
        graph[a].pb(b);
        graph[b].pb(a);
    }
    int k;
    cin >> k;
    vector<pii> bad(n, mp(0, 0));
    map<pii, pii> badE;
    for (int i = 0; i < k; ++i) {
        int sz;
        cin >> sz;
        vector<int> v(sz);
        for (auto &x : v) {
            cin >> x;
            --x;
        }
        for (int j = 0; j < sz; ++j) {
            bad[v[j]] = mp(sz, j);
            badE[mp(v[j], v[(j + 1) % v.size()])] = mp(sz, j);
            badE[mp(v[(j + 1) % v.size()], v[j])] = mp(sz, j);
        }
    }
    int T = n * 4;
    vector<int> d(n, 1e9);
    d[0] = 0;
    priority_queue<pii> q;
    q.push(mp(0, 0));
    vector<int> marked(n, false);
    auto ok = [&](int v, int t) {
        return (bad[v].f == 0 || (t % bad[v].f != bad[v].s));
    };
    while (!q.empty()) {
        int i = q.top().s;
        q.pop();
        if (marked[i]) {
            continue;
        }
        int t = d[i];
        marked[i] = true;
        for (auto &u : graph[i]) {
            if (ok(u, t + 1) && (badE[mp(i, u)].f == 0 || (t % badE[mp(i, u)].f != badE[mp(i, u)].s))) {
                if (d[u] > t + 1) {
                    d[u] = t + 1;
                    q.push(mp(-d[u], u));
                }
            }
        }
        t = d[i] + 1;   
        if (ok(i, t)) {
            for (auto &u : graph[i]) {
                if (ok(u, t + 1) && (badE[mp(i, u)].f == 0 || (t % badE[mp(i, u)].f != badE[mp(i, u)].s))) {
                    if (d[u] > t + 1) {
                        d[u] = t + 1;
                        q.push(mp(-d[u], u));
                    }
                }
            }
        }
    }
    if (d[n - 1] == 1e9) {
        cout << "impossible" << endl;
    } else {
        cout << d[n - 1] << endl;
    }
}

signed main() {
    #ifdef LOCAL
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    #else
        ios::sync_with_stdio(false);
        cin.tie(0);
    #endif
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 25
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20