import java.math.BigInteger;

//
// Source from: http://www.merriampark.com/perm.htm
//
public class PermutationGenerator {

	private int[] a;
	private BigInteger numLeft;
	private BigInteger total;

	public PermutationGenerator(int n) {

		if (n < 1)
			throw new IllegalArgumentException("Min 1");
		
		a = new int[n];
		total = getFactorial(n);
		reset();

	}

	public void reset() {

		for (int i = 0; i < a.length; i++)
			a[i] = i;
		
		numLeft = new BigInteger(total.toString());

	}

	public BigInteger getNumLeft() {
		return numLeft;
	}

	public BigInteger getTotal() {
		return total;
	}

	public boolean hasMore() {
		return numLeft.compareTo(BigInteger.ZERO) == 1;
	}

	private static BigInteger getFactorial(int n) {
		
		BigInteger fact = BigInteger.ONE;
		
		for (int i = n; i > 1; i--)
			fact = fact.multiply(new BigInteger(Integer.toString(i)));
		
		return fact;

	}

	public int[] getNext() {

		if (numLeft.equals(total)) {

			numLeft = numLeft.subtract(BigInteger.ONE);
			return a;

		}

		int temp;

		// Find largest index j with a[j] < a[j+1]
		int j = a.length - 2;
		while (a[j] > a[j + 1])
			j--;


		// Find index k such that a[k] is smallest integer
		// greater than a[j] to the right of a[j]
		int k = a.length - 1;
		while (a[j] > a[k])
			k--;

		// Interchange a[j] and a[k]
		temp = a[k];
		a[k] = a[j];
		a[j] = temp;

		// Put tail end of permutation after jth position in increasing order

		int r = a.length - 1;
		int s = j + 1;

		while (r > s) {
			temp = a[s];
			a[s] = a[r];
			a[r] = temp;
			r--;
			s++;
		}

		numLeft = numLeft.subtract(BigInteger.ONE);
		return a;

	}
}