241014 문제집

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer st = new StringTokenizer(br.readLine());
	StringBuilder sb = new StringBuilder();

	int nodeCount = Integer.parseInt(st.nextToken());
	int edgeCount = Integer.parseInt(st.nextToken());

	int[] indegree = new int[nodeCount + 1];
	List<List<Integer>> graph = new ArrayList<>();
	PriorityQueue<Integer> priorityQueue = new PriorityQueue<>();

	for (int i = 0; i <= nodeCount; i++) {
		graph.add(new ArrayList<>());
	}

	for (int i = 0; i < edgeCount; i++) {
		st = new StringTokenizer(br.readLine());
		int from = Integer.parseInt(st.nextToken());
		int to = Integer.parseInt(st.nextToken());
		indegree[to]++;
		graph.get(from).add(to);
	}

	for (int i = 1; i <= nodeCount; i++) {
		if (indegree[i] == 0) {
			priorityQueue.add(i);
		}
	}

	while (!priorityQueue.isEmpty()) {
		int current = priorityQueue.poll();
		sb.append(current).append(" ");

		for (int nextNode : graph.get(current)) {
			indegree[nextNode]--;
			if (indegree[nextNode] == 0) {
				priorityQueue.add(nextNode);
			}
		}
	}

	System.out.println(sb);
}

출처:https://www.acmicpc.net/problem/1766