Submission #400937

#	Time	Username	Problem	Language	Result	Execution time	Memory
400937		534351	From Hacks to Snitches (BOI21_watchmen)	C++17	0 / 100	68 ms	22852 KiB

watchmen

#include <bits/stdc++.h>

using namespace std;

template<class T, class U>
void ckmin(T &a, U b)
{
    if (a > b) a = b;
}

template<class T, class U>
void ckmax(T &a, U b)
{
    if (a < b) a = b;
}

#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define SZ(x) ((int) (x).size())
#define ALL(x) (x).begin(), (x).end()
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)

const int MAXN = 250013;
const int INF = 1e9 + 7;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;

int N, M, K;
vi edge[MAXN];
pii ban[MAXN];
map<int, pii> banedge[MAXN];
int dist[MAXN];
priority_queue<pii, vector<pii>, greater<pii> > pq;

int32_t main()
{
    cout << fixed << setprecision(12);
    cerr << fixed << setprecision(4);
    ios_base::sync_with_stdio(false); cin.tie(0);
    cin >> N >> M;
    FOR(i, 0, M)
    {
        int u, v;
        cin >> u >> v; u--; v--;
        edge[u].PB(v);
        edge[v].PB(u);
    }
    cin >> K;
    FOR(i, 0, K)
    {
        int c; cin >> c;
        vi s(c);
        FOR(j, 0, c)
        {
            cin >> s[j]; s[j]--;
            ban[s[j]] = {j, c};
        }
        FOR(j, 0, c)
        {
            int u = s[j], v = s[(j == c - 1 ? 0 : j + 1)];
            banedge[u][v] = {j, c};
            banedge[v][u] = {j, c};
            // cerr << u << ' ' << v << ' ' << j << ' ' << c << endl;
        }
    }
    fill(dist, dist + N, INF);
    dist[0] = 0;
    pq.push({0, 0});
    while(!pq.empty())
    {
        int d = pq.top().fi, u = pq.top().se; pq.pop();
        if (d != dist[u]) continue;
        for (int v : edge[u])
        {
            FOR(k, 1, 5)
            {
                int t = d + k;
                if (ban[u].se != 0 && (t - 1) % ban[u].se == ban[u].fi) continue;
                if (ban[v].se != 0 && t % ban[v].se == ban[v].fi) continue;
                if (banedge[u].count(v) && (t - 1) % banedge[u][v].se == banedge[u][v].fi) continue;
                if (t > dist[v]) continue;
                dist[v] = t;
                // cerr << u << ' ' << v << ' ' << t << endl;
                pq.push({dist[v], v});
                break;
            }
            //you can go from u -> v at time t iff:
            //t != ban[v].fi mod ban[v].se
            //t-1 != ban[u][v].fi mod ban[u][v].se
        }
    }
    if (dist[N - 1] >= INF)
    {
        cout << "impossible\n";
        return 0;
    }
    cout << dist[N - 1] << '\n';
    return 0;
}

• 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