Problem finding the GCD

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C#

Console.WriteLine("This is a program that calculates the gcd of some typed number");
            int StartingNum = Convert.ToInt16(Console.ReadLine());
            int NumForCalculate = StartingNum;
            string gcd = ("");
            int gathering = 1;
            operation:
            int x = 2;
            operation2:
            if ((NumForCalculate / x) == :see below:)
            {
                if (gcd == "")
                    gcd = ("" + x);
                else
                    gcd = (gcd + "," + x);
                NumForCalculate = (NumForCalculate / x);
                gathering = gathering * x;
                if (NumForCalculate <= 1)
                    goto end;
                else
                    goto operation;
            }
            else
            {
                x++;
                goto operation2;
            }
            end:
            Console.WriteLine("gcd of integers {0} is {1}, and gathering this set of numbers is {2}", StartingNum, gcd, gathering);
            Console.ReadKey();

if i set starting nub as 20

if ((NumForCalculate / x) == 1)

it will be like this: gcd of integers 20 is 11, and gathering this set of numbers is 11

if ((NumForCalculate / x) == 0)

it will be like this: gcd of integers 20 is 21, and gathering this set of numbers is 21

Posted 6-Apr-13 8:14am

Member 9967727

Updated 6-Apr-13 9:11am

Kenneth Haugland

v2

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Kenneth Haugland 6-Apr-13 14:38pm

Not quite related to your question but have you seen this:
http://msdn.microsoft.com/en-us/library/microsoft.solverfoundation.common.biginteger.gcd%28v=vs.93%29.aspx

Kenneth Haugland 6-Apr-13 14:41pm

And please remove the GoTo statements, they are usually considered ancient relics in the modern era.

OriginalGriff 6-Apr-13 14:54pm

Agreed - I'm not even looking at it with those in there...

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Kenneth Haugland · Accepted Answer · 2013-04-06T09:09:00

Solution 1

The problem of finding the GCD is usually done by using modular, i.a.

VB

if (20 Mod 2 = 0) then

or C#

C#

if (20%2==0)

This allows you to check if they could be devisible by a number without any remander. I have implemented sort of the thing you are looking for here:
Fun with continued fractions[^]

As for the GoTo statments, they should be removed becouse the make the code completely unreadeble. I usually reffer to this kind of code as Spaghetti-code, as you cant find the start or end of anything. And they are sure to frustrate you or even worse, the person that would take over your code.

Posted 6-Apr-13 9:09am

Kenneth Haugland

Comments

Kenneth Haugland 6-Apr-13 15:36pm

From op:
nah same things happend

if i set starting nub as 20

if ((NumForCalculate / x) == 1)

it will be like this: gcd of integers 20 is 11, and gathering this set of numbers is 11

if ((NumForCalculate / x) == 0)

it will be like this: gcd of integers 20 is 21, and gathering this set of numbers is 21

just like it was before

Kenneth Haugland 6-Apr-13 15:39pm

You didnt seem to understand me, use (NumForCalculate % x == 0). And this:
"it will be like this: gcd of integers 20 is 11, and gathering this set of numbers is 11"
seems that you are misunderstanding what GCD actually is.