Permutation

import java.util.ArrayList;

public class Perm {
	static char[] A = "ABCDEF".toCharArray();
	static int N = 6;
	static int R = 3;

	static ArrayList<String> list = new ArrayList<>();

	public static void main(String[] args) {
		nPr(0, new boolean[N]);
	}

	// 끝까지 검색하고 돌아와
	private static void nPr(int count, boolean[] b) {
		if (count == R) {
			System.out.println(list);
			return;
		}
		for (int i = 0; i < N; i++) {
			if (!b[i]) {
				b[i] = true;
				list.add(A[i] + " ");
				nPr(count + 1, b);
				b[i] = false;
				list.remove(A[i] + " ");
			}
		}
	}
}