[C++] 백준 18352번 특정 거리의 도시 찾기

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

18352번: 특정 거리의 도시 찾기

---

#include <bits/stdc++.h>
using namespace std;

int n, m, k, x;
int d[300003];
vector<int> v[300003];

// basic dijkstra form
void dijk(int s) {
	d[s] = 0;
	queue<int> q;
	q.push(s);
	while (!q.empty()) {
		int cur = q.front();
		q.pop();
		for (int i = 0; i < v[cur].size(); i++) {
			int next = v[cur][i];
			if (d[next] > d[cur] + 1) {
				d[next] = d[cur] + 1;
				q.push(next);
			}
		}
	}
}

int main()
{
	int i, from, to;
	cin >> n >> m >> k >> x;

	for (i = 1; i <= n; i++) {
		d[i] = 1e9;
	}

	for (i = 1; i <= m; i++) {
		cin >> from >> to;
		v[from].push_back(to);
	}

	dijk(x);
	bool check = false;

	for (i = 1; i <= n; i++) {
		if (d[i] == k) {
			check = true;
			cout << i << '\n';
		}
	}

	if (check == false) cout <<  "-1";

	return 0;
}