Submission #714278

#	Time	Username	Problem	Language	Result	Execution time	Memory
714278		vjudge1	Event Hopping (BOI22_events)	C++17	0 / 100	1589 ms	3148 KiB

events

#include <bits/stdc++.h>

#define ll long long
#define pii pair<int, int>
#define oo 1e9

using namespace std;

vector<vector<int>> g;
vector<bool> visited;
int dfs(int node, int target){
    if(node == target) return 0;
    visited[node] = 1;
    int ans = oo;
    for(int to:g[node]){
        if(visited[to]) continue;
        ans = min(ans, dfs(to, target) + 1);
    }
    visited[node] = 0;
    return ans;
}

int main(){
    int n, q; cin >> n >> q;
    vector<pii> v(n + 1);
    for (int i = 1; i <= n; i++)
    {
        cin >> v[i].first >> v[i].second;
    }
    if(n > 1000 || q > 100){
        while(q--){
            int i, j; cin >> i >> j;
            if(i == j){
                cout << 0 << '\n';
            }
            else if(v[i].second <= v[j].second && v[i].second >= v[j].first){
                cout << 1 << '\n';
            }
            else{
                cout << "impossible\n";
            }
        }
        return 0;
    }
    visited.resize(n + 1, 0);
    g.resize(n + 1);
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            if(i == j) continue;
            if(v[i].second <= v[j].second && v[i].second >= v[j].first){
                g[i].emplace_back(j);
            }
        }
    }
    
    while(q--){
        int u, v; cin >> u >> v;
        int ans = dfs(u, v);
        if(ans == oo){
            cout << "impossible\n";
        }
        else{
            cout << ans << '\n';
        }
    }
}

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30