백준 N과M(2)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;
 
public class Main {
    
    public static int[] arr ;
    public static int[] set;
    private static int r;
    
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");
        arr = new int[Integer.parseInt(st.nextToken())];
        r = Integer.parseInt(st.nextToken());
        set = new int[r];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = i+1;
        }
        
        c(0, 0 ,r);
        
    }
    
 
    
    
    public static void c(int len, int k, int r) {
        if(len==r) {
            for (int i = 0; i < set.length; i++) {
                System.out.print(set[i] + " ");
            }
            System.out.println();
            return;
        }
        
        for(int i=k;i<arr.length;i++) {
            set[len] = arr[i];
            c(len+1,i+1,r);
        }
    }
 
}