백준18352_특정 거리의 도시 찾기

-문제-

https://www.acmicpc.net/problem/18352

 

 

-코드-

#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;




void bfs(const vector<vector<int>>& adj, int s, vector<int>& dist){
    queue<int> q;
    q.push(s);
    dist[s] = 0;
    
    while(!q.empty()){
        int cur = q.front();
        q.pop();
        
        
        for(auto nxt: adj[cur]){
            if(dist[nxt] != -1) continue;
            
            dist[nxt] = dist[cur]+1;
            q.push(nxt);
        }
            
        }
    
    
}


int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int N, M, K, X;
    cin >> N >> M >> K >> X;
    
    vector<vector<int>> adj(N+1);
    
    while(M--){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
    }
    
    vector<int> dist(N+1, -1);
    
    bfs(adj, X, dist);
    
    vector<int> answer;
    for(int i = 1; i <=N; i++)
        if(dist[i] == K) answer.push_back(i);
        
    if(answer.empty()){
            cout << -1 <<"\n";
        }
    
    for(int j : answer){
        cout << j <<"\n";
    }
    
    
    return 0;
    

}