Submission #540484

#	Time	Username	Problem	Language	Result	Execution time	Memory
540484		elazarkoren	From Hacks to Snitches (BOI21_watchmen)	C++17	15 / 100	1282 ms	143256 KiB

watchmen

#include <bits/stdc++.h>
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define chkmin(a, b) a = min(a, b)
#define chkmax(a, b) a = max(a, b)
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vii;
typedef vector<bool> vb;

const int MAX_N = 1e5 + 5;
const int MAX_L = 1e4;
const int infinity = 1e9;

int Gcd(int a, int b) {
    return (b ? Gcd(b, a % b) : a);
}

inline int Lcm(int a, int b) {
    return a * b / Gcd(a, b);
}

set<int> bad_node[MAX_L];
set<pii> bad_edge[MAX_L];
//queue<pii> q;//[MAX_L];
bitset<MAX_N> visited[MAX_L];
//int dist[MAX_N][MAX_L];
int cycle[MAX_N];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    vvi graph(n + 1);
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    for (int i = 1; i <= n; i++) cycle[i] = 1;
    int k;
    cin >> k;
    vi len(k);
    vvi path(k);
    for (int j = 0; j < k; j++) {
        cin >> len[j];
        path[j].resize(len[j] + 1);
        for (int i = 0; i < len[j]; i++) {
            cin >> path[j][i];
            cycle[path[j][i]] = len[j];
        }
        path[j][len[j]] = path[j][0];
        for (int i = 1; i <= len[j]; i++) {
            bad_node[i % len[j]].insert(path[j][i]);
            bad_edge[i % len[j]].insert({min(path[j][i], path[j][i - 1]), max(path[j][i], path[j][i - 1])});
        }
    }
    bitset<MAX_N> vis;
    for (int i = 1; i <= n; i++) {
        if (cycle[i] == 1) {
            vis[i] = true;
            for (int neighbor : graph[i]) {
                if (!vis[neighbor]) cycle[i] = Lcm(cycle[i], cycle[neighbor]);
            }
        }
//        for (int j = 0; j < cycle[i]; j++) dist[i][j] = infinity;
    }
//    priority_queue<pii, vii, greater<pii>> pq;
    queue<pii> pq;
    pq.push({1, 0});
    while (!pq.empty()) {
        auto [node, d] = pq.front();
        pq.pop();
        if (visited[d % cycle[node]][node]) continue;
        visited[d % cycle[node]][node] = true;
        if (node == n) {
            cout << d << '\n';
            return 0;
        }
        if (!bad_node[(d + 1) % cycle[node]].count(node)) {
            if (!visited[(d + 1) % cycle[node]][node]) {
                pq.push({node, d + 1});
            }
//            if (d + 1 < dist[node][(d + 1) % cycle[node]]) {
//                dist[node][(d + 1) % cycle[node]] = d + 1;
//                pq.push({node, d + 1});
//            }
        }
        for (int neighbor : graph[node]) {
            if (!bad_node[(d + 1) % cycle[neighbor]].count(neighbor)) {
                if (!bad_edge[(d + 1) % cycle[neighbor]].count({min(node, neighbor), max(node, neighbor)})) {
                    if (!visited[(d + 1) % cycle[neighbor]][neighbor]) {
                        pq.push({neighbor, d + 1});
                    }
//                    if (d + 1 < dist[neighbor][(d + 1) % cycle[neighbor]]) {
//                        dist[node][(d + 1) % cycle[neighbor]] = d + 1;
//                        pq.push({neighbor, d + 1});
//                    }
                }
            }
        }
    }
    cout << "impossible\n";
    return 0;
}
//6 6
//1 2
//2 3
//3 4
//4 5
//5 6
//2 4
//1
//3 2 3 4

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