[알고리즘] 백준 - 15663 ( N과 M(9) ) / 자바

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

class Main {
	static int N, M;
	static int[] answer;
	static int[] arr;
	static boolean[] check;

	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());
		M = Integer.parseInt(st.nextToken());
		answer = new int[M];
		check = new boolean[N];
		arr = new int[N];
		
		st = new StringTokenizer(br.readLine());
		for (int i = 0; i < N; i++) {
			arr[i] = Integer.parseInt(st.nextToken());
		}
		Arrays.sort(arr);
		perm(0);
		System.out.println(sb);
	}

	private static void perm(int count) {
		if (count == M) { //원하는 만큼 뽑았으면 탈출
			for (int i = 0; i < M; i++) {
				sb.append(answer[i]).append(" ");

			}
			sb.append("\n");
			return;
		} else {
			int before = 0; // 이전에 뽑았던 값을 저장 
			for (int i = 0; i < N; i++) {
				if (check[i]) {  // 뽑았던 값이면 
					continue;
				} else if (before != arr[i] ) {
					check[i] = true;
					answer[count] = arr[i];
					before = arr[i];
					perm(count + 1);
					check[i] = false;
				}
			}
		}
	}
}

헤매긴 했지만 어찌어찌 성공했다.