JAVA ac代码:

import java.util.*;
import java.util.StringTokenizer;
import java.io.*;

public class Main {
    static int n,m;
    public static void main(String[] args) {
        n=in.nextInt();m=in.nextInt();
        int[] arr=new int[m+10];
        dfs(arr,1,0);
        out.close();
    }
    



    private static void dfs(int[] arr,int i, int count) {
        //i越界或者剩余的i不足够填满m个数字
        if(i>n+1||count+(n-i)<m-2)return;
    
        //如果count==m，数量够了就输出
        if(count==m) {
            for(int j=0;j<m;j++) out.print(arr[j]+" ");
            out.println();
            return;
        }
        arr[count]=i;
        dfs(arr,i+1,count+1);
        arr[count]=0;
        dfs(arr,i+1,count);
        
    }




    static FastReader in=new FastReader();
    static PrintWriter out=new PrintWriter(System.out);
    static class FastReader{
        static BufferedReader br;
        static StringTokenizer st;
        FastReader(){
            br=new BufferedReader(new InputStreamReader(System.in));
        }
        String next() {
            String str="";
            while(st==null||!st.hasMoreElements()) {
                try {
                    str=br.readLine();
                }catch(IOException e) {
                    throw new RuntimeException(e);
                }
                st=new StringTokenizer(str);
            }
            return st.nextToken();
        }
        int nextInt() {
            return Integer.parseInt(next());
        }
        double nextDouble() {
            return Double.parseDouble(next());
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }
    
}