230926 가장 먼 노드

public int solution(int n, int[][] edge) {
	int answer = 0;

	List<Integer>[] adj = new ArrayList[n + 1];
	for (int i = 1; i <= n; i++) {
		adj[i] = new ArrayList<>();
	}

	for (int[] e : edge) {
		adj[e[0]].add(e[1]);
		adj[e[1]].add(e[0]);
	}

	int[] depths = bfs(adj);

	int maxDepth = Arrays.stream(depths).max().getAsInt();
	answer = (int) Arrays.stream(depths).filter(depth -> depth == maxDepth).count();

	return answer;
}

private int[] bfs(List<Integer>[] adj) {
	int n = adj.length - 1;
	int[] depths = new int[n + 1];
	boolean[] visited = new boolean[n + 1];

	Queue<Integer> queue = new LinkedList<>();
	queue.add(1);
	visited[1] = true;

	while (!queue.isEmpty()) {
		int node = queue.poll();

		for (int neighbor : adj[node]) {
			if (!visited[neighbor]) {
				visited[neighbor] = true;
				depths[neighbor] = depths[node] + 1;
				queue.add(neighbor);
			}
		}
	}

	return depths;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/49189