# question on iteration

Ricky James

Ranch Hand

Posts: 83

posted 9 years ago

Hello,

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

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

Shall be extremely grateful.

Thanks

Ricky

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.

Shall be extremely grateful.

Thanks

Ricky

Shashi Kant

Ranch Hand

Posts: 117

Ricky James

Ranch Hand

Posts: 83

posted 9 years ago

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

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

Ranch Hand

Posts: 117

Ricky James

Ranch Hand

Posts: 83

posted 9 years ago

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

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

Ranch Hand

Posts: 117

Ricky James

Ranch Hand

Posts: 83

posted 9 years ago

Perfect!

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

Brilliant.

Thanks

Ricky

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