# question on iteration

Ricky James

Ranch Hand

Posts: 83

posted 8 years ago

- 0

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

posted 8 years ago

- 0

Hello Ricky

In your code

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

In your code

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

If it's true that we are here to help others, then what exactly are the others here for?

Ricky James

Ranch Hand

Posts: 83

posted 8 years ago

- 0

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 8 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

- 0

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 8 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

- 0

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