https://www.acmicpc.net/problem/15649

N과 M (1).java

import java.util.*;

public class Main {
    
    static int N, M;
    static int []num;
    static boolean []visited;
    static StringBuilder sb = new StringBuilder();
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        N = sc.nextInt();
        M = sc.nextInt();    
        sc.close();
        num = new int[N+1];
        visited = new boolean[N+1];
        bt(0);
        System.out.print(sb);
    }

    static void bt(int count){
        if (count == M) {
            for (int i=0; i<M; i++)
                sb.append(num[i]+" ");
            sb.append("\n");
            return;        
        }
        for (int i=1; i<=N; i++){
            if(!visited[i])
            {
                visited[i] = true;
                num[count] = i;
                bt(count+1);
                visited[i] = false;
            }
        }
    }
}