240923 트리와 쿼리

static int[] size;
static List<Integer>[] adjList;

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

	int nodeCount = Integer.parseInt(st.nextToken());
	int root = Integer.parseInt(st.nextToken());
	int queryCount = Integer.parseInt(st.nextToken());

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

	size = new int[nodeCount + 1];

	for (int i = 1; i < nodeCount; i++) {
		st = new StringTokenizer(br.readLine());
		int start = Integer.parseInt(st.nextToken());
		int end = Integer.parseInt(st.nextToken());
		adjList[start].add(end);
		adjList[end].add(start);
	}

	calculateSubtreeSize(root, 0);

	for (int i = 0; i < queryCount; i++) {
		int queryNode = Integer.parseInt(br.readLine());
		sb.append(size[queryNode]).append('\n');
	}
	System.out.print(sb);
}

static void calculateSubtreeSize(int currentNode, int parentNode) {
	size[currentNode] = 1;
	for (Integer childNode : adjList[currentNode]) {
		if (childNode != parentNode) {
			calculateSubtreeSize(childNode, currentNode);
			size[currentNode] += size[childNode];
		}
	}
}

출처:https://www.acmicpc.net/problem/15681