/*
 * Compute factorials recursively.
 * One on the way into the recursion, once on the way out
 * In is often more efficient, but requires can require extra parameters
 * @author ggtowell
 * Created: Oct 27, 2023
*/

public class Factorial {
    public static void main(String[] args) {
        factSending(5, 1);
        factReturning(5);
    }

    /**
     * Recursively on the way out
     * @param num
     * @return
     */
    public static int factReturning(int num) {
        if (num == 1) {
            return 1;
        }
        return num * factReturning(num - 1);
    }

    /**
     * Recursively on the way in
     * @param num
     * @param res
     * @return
     */
    public static int factSending(int num, int res) {
        if (num == 1) {
            return res;
        }
        return factSending(num - 1, res * num);
    }
}