코드 질문입니다.

public class Main {
	
	static int n;
	static int m;
	static Queue<String> Q;
	
	public void BFS(String str) {
		Q = new LinkedList<>();
		Q.offer(str);
		int L = 0;
		
		while(!Q.isEmpty()) {
			int len = Q.size();
			for(int i=0; i<len; i++) {
				String tmp = Q.poll();
				for(int j=1; j<=n; j++) {
					if(tmp == "0") Q.offer(String.valueOf(j));
					else Q.offer(tmp+" "+String.valueOf(j));
				}
			}
			L++;
			if(L==m) return;
		}
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Main T = new Main();
		Scanner kb = new Scanner(System.in);
		n = kb.nextInt();
		m = kb.nextInt();
		
		T.BFS("0");
		for(String x:Q) {
			System.out.println(x);
		}
	}
}