How to write a simple Java program that finds the

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How to find GCD, LCM on a set of numbers (13 answers)

Closed 5 years ago.

Here is the question:

"Write a method named gcd that accepts two integers as parameters and returns the greatest common divisor of the two numbers. The greatest common divisor (GCD) of two integers a and b is the largest integer that is a factor of both a and b. The GCD of any number and 1 is 1, and the GCD of any number and 0 is that number.

One efficient way to compute the GCD of two numbers is to use Euclid's algorithm, which states the following:

GCD(A, B) = GCD(B, A % B) 
GCD(A, 0) = Absolute value of A"

I'm really confused as to how to solve this problem. I just want some hints and tips as to what I did wrong in the program I have so far. (I have to put in a Scanner, that is my teacher's requirement.) Don't give me a full code as I kinda want to solve this out myself. Maybe just give me a hint on how I incorporate this formula that you see above. (And if you're wondering why I put in the == 0, it's because I thought that if you have two numbers, say 0 and 90, their GCD would be 0 right??)

Also, my code has to include while loops...I would've preferred if loops...

Thanks in advance! :)

My current program:

public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int a = console.nextInt();
        int b = console.nextInt();
        gcd (a, b);
    }

    public static void gcd(int a, int b) {
        System.out.print("Type in two numbers and I will print outs its Greatest Common Divisor: ");
        int gcdNum1 = console.nextInt();
        int gcdNum2 = console.nextInt();
        while (gcdNum1 == 0) {
            gcdNum1 = 0;
        }
        while (gcdNum2 > gcdNum1) {
            int gcd = gcdNum1 % gcdNum2;
        }
        System.out.print(gcdNum1 + gcdNum2);
    }
}

Answer 1

private static void GCD(int a, int b) {

    int temp;
    // make a greater than b
    if (b > a) {
         temp = a;
         a = b;
         b = temp;
    }

    while (b !=0) {
        // gcd of b and a%b
        temp = a%b;
        // always make a greater than bf
        a =b;
        b =temp;

    }
    System.out.println(a);
}

Answer 2

public static int GCD(int x, int y) {   
    int r;
    while (y!=0) {
        r = x%y;
        x = y;
        y = r;
    }
    return x;
}