Permutation and combination of 2 numbers

The given Java code calculates the permutation and combination of two numbers n and r.

fact function is used to calculate the factorial of a number, which is defined as the product of all positive integers less than or equal to that number. If the value of val is 0 or 1, the function returns 1. For any other value of val, the function returns the product of val and the factorial of val-1.

main method takes two inputs, n and r, from the user and calculates the combination and permutation of the two numbers. The combination is calculated by dividing the factorial of n by the product of the factorials of r and n-r. The permutation is calculated by dividing the factorial of n by the factorial of n-r.

Finally, the calculated values of combination and permutation are displayed to the user.

import java.util.Scanner;

public class PermutationCombination {
	private static int fact(int val) {
		if (val == 0 || val == 1)
			return 1;
		else
			return val * fact(val - 1);
	}

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n, r, combination, permutation;

		System.out.print("Enter value of n : ");
		n = scan.nextInt();
		System.out.print("Enter value of r : ");
		r = scan.nextInt();

		combination = fact(n) / (fact(r) * fact(n - r));
		permutation = fact(n) / fact(n - r);

		System.out.println("\nCombination : " + combination);
		System.out.print("Permutation : " + permutation);
	}
}

Output

Enter value of n : 8
Enter value of r : 6

Combination : 28
Permutation : 20160