[20251206] BOJ / G2 / 환승 / 권혁준

Author: oncsr

khj20006/202512/06 BOJ G2 환승.md

@@ -0,0 +1,44 @@
+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+const int INF = 1e9 + 7;
+
+int N, K, M;
+vector<vector<int>> v(101001);
+
+int bfs01(int start, int end) {
+	vector<int> dist(101001, INF);
+	deque<pair<int, int>> q;
+	dist[start] = 1;
+	q.emplace_back(1, start);
+	while (!q.empty()) {
+		auto [d, n] = q.front(); q.pop_front();
+		for (int i : v[n]) {
+			int cost = i > N ? 0 : 1;
+			if (dist[i] > d + cost) {
+				dist[i] = d + cost;
+				if (cost) q.emplace_back(dist[i], i);
+				else q.emplace_front(dist[i], i);
+			}
+		}
+	}
+	return dist[end] == INF ? -1 : dist[end];
+}
+
+int main() {
+	cin.tie(0)->sync_with_stdio(0);
+
+	cin >> N >> K >> M;
+	for (int i = 1; i <= M; i++) {
+		for (int j = 1, a; j <= K; j++) {
+			cin >> a;
+			v[a].push_back(N + i);
+			v[N + i].push_back(a);
+		}
+	}
+
+	cout << bfs01(1, N);
+
+}
+```