240823 로고

static class Rec {
	int x1;
	int y1;
	int x2;
	int y2;

	public Rec(int x1, int y1, int x2, int y2) {
		this.x1 = x1;
		this.y1 = y1;
		this.x2 = x2;
		this.y2 = y2;
	}
}

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

	int n = Integer.parseInt(br.readLine());
	Rec[] rectangles = new Rec[n + 1];
	boolean[] visited = new boolean[n + 1];
	Queue<Integer> queue = new LinkedList<>();
	int groups = 0;

	rectangles[0] = new Rec(0, 0, 0, 0);

	for (int i = 1; i <= n; i++) {
		StringTokenizer st = new StringTokenizer(br.readLine());
		int x1 = Integer.parseInt(st.nextToken());
		int y1 = Integer.parseInt(st.nextToken());
		int x2 = Integer.parseInt(st.nextToken());
		int y2 = Integer.parseInt(st.nextToken());
		rectangles[i] = new Rec(x1, y1, x2, y2);
	}

	for (int i = 0; i <= n; i++) {
		if (visited[i])
			continue;

		queue.add(i);
		visited[i] = true;

		while (!queue.isEmpty()) {
			int current = queue.poll();
			for (int j = 0; j <= n; j++) {
				if (!visited[j] && intersects(rectangles[current], rectangles[j])) {
					visited[j] = true;
					queue.add(j);
				}
			}
		}
		groups++;
	}
	System.out.println(groups - 1);
}

private static boolean intersects(Rec a, Rec b) {
	return !(a.x2 < b.x1 || b.x2 < a.x1 || a.y2 < b.y1 || b.y2 < a.y1)
			&& !(a.x1 > b.x1 && b.x2 > a.x2 && a.y1 > b.y1 && b.y2 > a.y2)
			&& !(a.x1 < b.x1 && b.x2 < a.x2 && a.y1 < b.y1 && b.y2 < a.y2);
}

출처:https://www.acmicpc.net/problem/3108