Submission #540456

#	Time	Username	Problem	Language	Result	Execution time	Memory
540456		elazarkoren	From Hacks to Snitches (BOI21_watchmen)	C++17	5 / 100	550 ms	9912 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 = 130;

int bad_node[MAX_L];
pii bad_edge[MAX_L];
queue<pii> q[MAX_L];
bitset<MAX_N> visited[MAX_L];

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);
    }
    int k, l;
    cin >> k >> l;
    vi path(l + 1);
    for (int i = 0; i < l; i++) {
        cin >> path[i];
        bad_node[i] = path[i];
    }
    path[l] = path[0];
    for (int i = 1; i <= l; i++) {
        bad_edge[i] = {min(path[i], path[i - 1]), max(path[i], path[i - 1])};
    }
    bad_edge[0] = bad_edge[l];
    q[0].push({1, 0});
    for (int i = 0; ; i++) {
        if (i == l) i = 0;
        if (q[i].empty()) break;
        int t = (i + 1) % l;
        while (!q[i].empty()) {
            auto [node, d] = q[i].front();
            if (node == n) {
                cout << d << '\n';
                return 0;
            }
            q[i].pop();
            if (!visited[t][node] && bad_node[t] != node) {
                visited[t][node] = true;
                q[t].push({node, d + 1});
            }
            for (int neighbor : graph[node]) {
                if (!visited[t][neighbor] && bad_node[t] != neighbor) {
                    if (bad_edge[t] != pii{min(node, neighbor), max(node, neighbor)}) {
                        visited[t][neighbor] = true;
                        q[t].push({neighbor, d + 1});
                    }
                }
            }
        }
    }
    cout << "impossible\n";
    return 0;
}
//6 6
//1 2
//2 3
//3 4
//4 5
//5 2
//5 6
//1
//4 3 2 5 4

• Subtask 1: 5 / 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