백준_15650_N과M(2)

https://www.acmicpc.net/problem/15650

간단한 조합 문제

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

public class Main {
    static int N, M;
    static int[] arr;
    static boolean[] selected;
    static StringBuilder sb = new StringBuilder();

    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());
        arr = new int[N + 1];
        selected = new boolean[N + 1];

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

        for(int i = 1; i <= N; i++){
            arr[i] = i;
        }

        combination(1, 0);
        System.out.print(sb);
    }

    static void combination(int idx, int size) {
        if (size == M) {
            for(int i = 1; i <= N; i++){
                if(selected[i]) sb.append(arr[i]).append(" ");
            }
            sb.append("\n");
            return;
        }

        for(int i = idx; i <= N; i++){

            if(selected[i]) continue;

            selected[i] = true;
            combination(i + 1, size + 1);

            selected[i] = false;
        }
    }
}

배열 원소 입력 잘 받았나 확인

System.out.println(Arrays.toString(arr));