package recursion;

/**
 *
 * @author Lefteris Moussiades
 */
public class IntroToRecursion {

    static void endless(int i) {
        System.out.println(i);
        if (i<10) endless(i + 1);
    }

    static void prt(int i) { // prt(1)= 1 {prt 2} 1 = 1 {2 {prt 3} 2} 1=1 2 3 3 2 1
        System.out.println(i);
        if (i < 3) {
            prt(i + 1);
        }
        System.out.println(i);
    }

    static int power(int b, int e) { //e>=0
        int rVal = 1;
        for (int i = 1; i <= e; i++) {
            rVal = rVal * b;
        }
        return rVal;
    }

    static int powerR(int b, int e) { //e>=0 
        if (e == 0) {
            return 1;
        } else {
            return powerR(b, e - 1) * b; //2^3=2^2*2=4*2=8
        }                                //2^2=2^1*2=2*2=4   
    }                                   //2^1=2^0*2=2
                                        //2^0=1    

    static int fibonacci(int k) { //1,1,2,3,5,8
        if (k <= 1) {
            return k;
        } else {
            return fibonacci(k - 1) + fibonacci(k - 2);
        }
    }
    
    //f(5)=f(4)+f(3)=f(3)+f(2)+f(2)+f(1)=f(1)+f(2)+f(0)+f(1)+f(0)+f(1)+1=1+f(0)+f(1)+1+1=4

    static int factorialR(int n) { //n!=(1*2*3...*n-1*)*n
        if (n == 0 || n == 1) { //4!=3!*4=(2!*3)*4=((1!*2)*3)*4=1*2*3*4=24
            return 1;
        } else {
            return factorialR(n - 1) * n;
        }
    }

    public static void main(String[] args) {
        endless(5);
        //prt(8);
        //System.out.println(fibonacci(5));
        //System.out.println(factorialR(19));

        //int k = powerR(2, 3);
        //System.out.println(k);

    }

}