boj_15650.java

package backtracking;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class boj_15650 {
    static int N;
    static int M;
    static int[] arr;
    static boolean[] check;
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());

        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());

        arr = new int[M+1];
        check = new boolean[N+1];

        dfs(1,0);
    }

    public static void dfs(int a,int dpt){
        if (dpt==M){
            for (int i = 0; i < M; i++) {
                System.out.print(arr[i] + " ");
            }
            System.out.println();
            return;
        }
        for(int i=a;i<=N;i++){
            arr[dpt]=i;
            dfs(i+1,dpt+1);
        }
    }
}