240417 줄세우기

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

	int numOfVertices = Integer.parseInt(st.nextToken());
	int numOfEdges = Integer.parseInt(st.nextToken());

	List<Integer>[] adjacencyList = new ArrayList[numOfVertices + 1];
	int[] indegrees = new int[numOfVertices + 1];
	StringBuilder result = new StringBuilder();

	for (int i = 1; i <= numOfVertices; i++) {
		adjacencyList[i] = new ArrayList<>();
	}

	for (int i = 0; i < numOfEdges; i++) {
		st = new StringTokenizer(br.readLine());
		int from = Integer.parseInt(st.nextToken());
		int to = Integer.parseInt(st.nextToken());

		adjacencyList[from].add(to);
		indegrees[to]++;
	}

	performTopologicalSort(adjacencyList, indegrees, result);
	System.out.println(result);
}

static void performTopologicalSort(List<Integer>[] adjacencyList, int[] indegrees, StringBuilder result) {
	Queue<Integer> queue = new LinkedList<>();

	for (int i = 1; i < adjacencyList.length; i++) {
		if (indegrees[i] == 0) {
			queue.add(i);
		}
	}

	while (!queue.isEmpty()) {
		int currentVertex = queue.poll();
		result.append(currentVertex).append(" ");

		for (int adjacentVertex : adjacencyList[currentVertex]) {
			indegrees[adjacentVertex]--;
			if (indegrees[adjacentVertex] == 0) {
				queue.add(adjacentVertex);
			}
		}
	}
}

출처:https://www.acmicpc.net/problem/2252