import java.util.*;

public class PermutationSeating3 {

    static int count;

    public static void main (String[] argv)
    {
        // Test case 1.
	int numSeats = 3;
	int numPeople = 2;
	int[] seats = new int [numSeats];
	count = 0;
	printPermutations (numSeats, numPeople, seats, 1);
	System.out.println ("  => " + count + " permutations");

        // Test case 2.
	numSeats = 5;
	numPeople = 2;
	seats = new int [numSeats];
	count = 0;
	printPermutations (numSeats, numPeople, seats, 1);
	System.out.println ("  => " + count + " permutations");
    }

    static void printPermutations (int numSpaces, int numRemaining, int[] seats, int person)
    {
	if (numRemaining == 0) {
	    System.out.println ( Arrays.toString(seats) );
	    count ++;
	    return;
	}

	// Look for an empty spot.
	for (int i=0; i<seats.length; i++) {
	    if (seats[i] == 0) {

                // Make a copy so that we don't need to un-do.
		int[] seatsCopy = copy (seats);

                // Assign and recurse.
		seatsCopy[i] = person;

		printPermutations (numSpaces-1, numRemaining-1, seatsCopy, person+1);
		// Don't need this: seats[i] = 0;
	    }
	}
    }

    static int[] copy (int[] A)
    {
	int[] B = new int [A.length];
	for (int i=0; i<A.length; i++) {
	    B[i] = A[i];
	}
	return B;
    }

}