CODEWITHSUNDEEP
javaloopswhile-loopsystem.outdate-arithmetic
billy
billy

Reputation: 1493

Why isn't my "While Loop" computing and printing out a simple 3N+1 equation?

So I had to write a simple code that would compute the 3N+1 equation; where N is an integer user types in and if it is a positive integer than N = N / 2 and if negative integer than N = N * 3 + 1.

However from what I can understand, my code doesn't work after the first while loop and hence prints nothing. What am I doing wrong? New to programming and still learning so I appreciate your help :)

Code:

import java.util.Scanner; 
public class ThreeNplusOneProgram {

    public static void main(String[] args) {

        int N; Scanner input = new Scanner(System.in); int counter; 

        System.out.println("Please Enter an integer: ");
        N = input.nextInt();

        while ( N <= 0 ) {
            System.out.println("ERROR: Please Enter an integer greater than zero: ");
            N = input.nextInt();
        }

        //So far we know that N is great than Zero

        System.out.println(N);
        counter = 1;
        while ( N != 1 ) { 

            if (N == N % 2 )
                N = N / 2; 

            else N = N * 3 + 1; 

            counter = counter + 1; 

        }

        System.out.println("There were" + counter + "terms in the sequence");
    }

}

Upvotes: 0

Views: 135

Answers (2)

Voidpaw
Voidpaw

Reputation: 920

The problem is your if (N == N % 2), you might just want to check if (N >= 0) since you do state that you are looking to check if it is a positive integer.

Upvotes: 0

LeeNeverGup
LeeNeverGup

Reputation: 1114

That is wrong: if (N == N % 2 ) N % 2 returns 1 or 0. You should use if (0 == N % 2 ) to check for being odd / even.

Upvotes: 5

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