Thread: Rewriting a method recursivly

Hello!

Consider this code

public static boolean isPower(int x, int n) {
 
    if (x == 1)
        return (n == 1);
 
    int pow = 1;
    while (pow < n)
        pow = pow * x;
 
 
    return (pow == n);
}

The goal is to find if the number x is a power of the number n.I've come up with this algorithm,and it works.I'd like to solve it recursivly as well,but I cannot come up with a good idea to start.

Thanks for the replies.

Originally Posted by Norm

Can you use integer division in the problem? If so, there is a much simpler solution.

Actually I've solved it already,like this.I dont need to solve it recursivly I want to solve it recursivly.To be precise I want to be able to "transform" iterative code into recursive,to figure out how to do that.

If integer division is part of that recursive solution than sure,anything is allowed.

Originally Posted by Norm

I don't see how to do it without passing x, n and pow to the method.

I found online how to transform iteration into recursion,followed the guide (its literally a pattern you have to follow).And I solved the problem.For those are interested;

public static boolean isPower_recursive(int x,int n) {
    if(x == 1)
        return (n==1);
    return isPower_recursion( x, n, 1);
 
    }
    public static boolean isPower_recursion(int x,int n, int pow) {
    if( pow > n) {
        return (pow == n);
    }
    pow = pow * x;
    return isPower_recursion(x,n,pow);
 
}

Originally Posted by Norm

Thanks for posting your solution. I see that the code passes 3 variables to the recursive method.

Yea,also a little typo from me.

public class test {
	public static void main(String[] args) {
		System.out.println(isPower_recursive(2,16));
 
 
}
 
public static boolean isPower(int x, int n) {
        if (x == 1)//header
            return (n == 1);//header
 
 
        int pow = 1;//header
        while (pow < n) {//loop
            pow = pow * x;// loop body
 
		}
        return (pow == n); //return statement
    }
 
	public static boolean isPower_recursive(int x,int n) {
    if(x == 1)
        return (n==1);
    return isPower_recursion( x, n, 1);
 
    }
    public static boolean isPower_recursion(int x,int n, int pow) {
    if( pow >= n) {
        return (pow == n);
    }
    pow = pow * x;
    return isPower_recursion(x,n,pow);
 
}
}

Its >= not >.