[BOJ] 15649 N과 M (1) 실버3

package day0803;

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

public class Main {
	static int N;
	static int M;
	static int[] arr;
	static boolean[] visit;
	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());
		arr = new int[M];
		visit = new boolean[N];
		dfs(0);
		System.out.println(sb);
	}

	private static void dfs(int dep) {
		if (dep == M) {
			for (int i : arr) {
				sb.append(i).append(" ");
			}
			sb.append("\n");
			return;
		}
		for (int i = 0; i < N; i++) {
			if (!visit[i]) {
				visit[i] = true;
				arr[dep] = i + 1;
				dfs(dep + 1);
				visit[i] = false;
			}
		}
	}
}

순열.. dfs .. 아직 완벽하게 숙지는 못한것 같다.
조금 더 하면 익숙해질듯