특정 거리의 도시 찾기

#include <iostream> #include <vector> #include <queue> #define endl "\n" #define INF 3000000 int distance[300001]; std::vector<int> graph[300001]; std::priority_queue<std::pair<int, int> > pq; int N, M, K, X; void io_faster() { std::ios_base::sync_with_stdio(false); std::cin.tie(0); std::cout.tie(0); } void input() { int node1, node2; io_faster(); std::cin >> N >> M >> K >> X; for (int i = 0 ; i < M ; i++) { std::cin >> node1 >> node2; graph[node1].push_back(node2); } for (int i = 1 ; i <= N ; i++) distance[i] = INF; } void solve() { int current, d, c_size, next, next_cost, fl = 0; distance[X] = 0; pq.push({0, X}); while(!pq.empty()) { d = -pq.top().first; current = pq.top().second; pq.pop(); c_size = graph[current].size(); if (d > distance[current]) continue; for (int i = 0 ; i < c_size ; i++) { next = graph[current][i]; next_cost = d + 1; if (next_cost > distance[next]) continue; distance[next] = next_cost; pq.push({-next_cost, next}); } } for (int i = 1 ; i <= N ; i++) { if (distance[i] == K) { std::cout << i << endl; fl = 1; } } if (!fl) std::cout << -1; } int main() { input(); solve(); return (0); }