I am practicing iteration from a book and it has the following ex:

The greatest common factor (GCF) of two numbers is the largest number that evenly divides both numbers. Using Euclid�s method, create two codes for computing the GCF of two numbers. Use iteration for the first code and recursion for the other one. Notes on Euclid�s algorithm: 1. Get input integers x and y. 2. Repeat the following step while y != 0 a. y = x % y; b. x = old value of y 3. Return x. For example, x = 14 and y = 6. y = x % y = 14 % 6 = 2 x = 6 y = x % y = 6 % 2 = 0 x = 2 (GCF)

I tried this code with iteration and I am pasting it here:

public class ExerciseOne {

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

public static void main(String args[]){ System.out.println(GCF(14,6)); } }

Now I know the answer to this exercise is 2 and I am doing something fundamentally wrong. Can anyone please point out what is the problem with my code?

I can see that x doesn't get the 'old value' of y. But I don't know how I can do it.

you are assigning the value of y to x after changing the orginal value of y i.e.

So modify your code like By this you will get the old value of y.

Regards Shashikant

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Ricky James
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Joined: Mar 26, 2007
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Hello Shashikant,

Thanks for the reply. I tried what you advised but even that gives me an error.

When I assign the value of y into x before the statement y = x % y I get the answer 6 which is the value of y so that means that the new value never gets assigned, and x takes the original value of y.

Ricky

Shashi Kant
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Joined: Aug 08, 2006
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Hello Ricky

Instead of returning the value of x why can't you return value of y directly.

Regards Shashikant

Ricky James
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Originally posted by Shashikant Dahatonde: Hello Ricky

Instead of returning the value of x why can't you return value of y directly.

Regards Shashikant

Hi Shashikant,

I am trying to follow the requirements of the exercise. And they state the pseudocode that is to be followed.

I know this can be done using recursion as well and that is the next step of the exercise. But first I want to do the way the exercise suggests.

Thanks Ricky

Shashi Kant
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Joined: Aug 08, 2006
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Hi Ricky

Sorry please ignore my previous post. Just try the following code Hope this will help you

Regards Shashikant

Ricky James
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Joined: Mar 26, 2007
Posts: 83

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Originally posted by Shashikant Dahatonde: Hi Ricky

Sorry please ignore my previous post. Just try the following code Hope this will help you

Regards Shashikant

Perfect! It worked. So basically we store the value in a 'temp' variable and then assign that value into x. Brilliant.

Thanks Ricky

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