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**Batcher****Member**- Registered: 20 Jul 2015
- Posts: 56

Hi everyone

I would like to greater a batch file that allows the user to enter 2 or three numbers and the file echo's the GCF of the numbers so if the user enters

```
3
6
```

The code displays

`3`

If the user inputs

```
25
50
100
```

The code will echo

`25`

Thanks ~Batcher

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**Aacini****Member**- Registered: 05 Dec 2012
- Posts: 116

Are you asking us for the method used to get the GCF of two or three numbers? You may review it from this Wikipedia page.

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**Batcher****Member**- Registered: 20 Jul 2015
- Posts: 56

Aacini wrote:

Are you asking us for the method used to get the GCF of two or three numbers? You may review it from this Wikipedia page.

I was looking for a batch file that could do this Im sure there is a more efficient way than what I'm trying

```
Set /a num=input/2
Set /a numa=num*2
if %num% EQU %input% set divisora="2, "
Set /a num=input/3
Set /a numa=num*3
if %num% EQU %input% set divisorb="3, "
Set /a num=input/4
Set /a numa=num*4
if %num% EQU %input% set divisorc="4, "
:: and so on
Echo %divisora%%divisorb%%divisorc%................................
```

*Last edited by Batcher (05 Nov 2016 14:52)*

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**Aacini****Member**- Registered: 05 Dec 2012
- Posts: 116

Ok. I read the Wikipedia article and chose the Binary method, so I copied this section:

```
Input: a, b positive integers
Output: g and d such that g is odd and gcd(a, b) = g×2d
d := 0
while a and b are both even do
a := a/2
b := b/2
d := d + 1
while a ≠ b do
if a is even then a := a/2
else if b is even then b := b/2
else if a > b then a := (a – b)/2
else b := (b – a)/2
g := a
output g, d
```

... into a Batch file and just inserted the modifications required in order to convert the operations into valid (and efficient) Batch code. This is the result:

```
@echo off
setlocal
:loop
set "num1="
set /P "num1=Enter first number: "
if not defined num1 goto endLoop
set "num2="
set /P "num2=Enter second number: "
if not defined num2 goto endLoop
call :gcd %num1% %num2%
goto loop
:endLoop
goto :EOF
:gcd
rem Input: a, b positive integers
set /A "a = %1, b = %2, d = 0, aANDbEVEN = (a&1) + (b&1)"
:while1 a and b are both even do
if %aANDbEVEN% neq 0 goto endwhile1
set /A "a >>= 1, b >>= 1, d += 1, aANDbEVEN = (a&1) + (b&1)"
goto while1
:endwhile1
:while2 a NEQ b do
if %a% equ %b% goto endwhile2
set /A "aIsEven = a&1, bIsEven = b&1"
if %aIsEven% equ 0 ( set /A "a >>= 1"
) else if %bIsEven% equ 0 ( set /A "b >>= 1"
) else if %a% GTR %b% ( set /A "a = (a - b)/2"
) else set /A "b = (b - a)/2"
goto while2
:endwhile2
rem Output: g and d such that g is odd and gcd(a, b) = g×2^d
rem g := a
rem output g, d
set /A "gcd = a * (1<<d)"
echo The GCD is %gcd%
echo/
exit /B
```

Antonio

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**Batcher****Member**- Registered: 20 Jul 2015
- Posts: 56

Thank you!

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**Batcher****Member**- Registered: 20 Jul 2015
- Posts: 56

Could I find the GCF between three numbers I tried modifying the code but I'm not sure if I did it correctly. The bottom portion is also a bit complicated so I wasn't sure how to change anything there.

```
@echo off
setlocal
:loop
set "num1="
set /P "num1=Enter first number: "
if not defined num1 goto endLoop
set "num2="
set /P "num2=Enter second number: "
if not defined num2 goto endLoop
set "num3="
set /P "num3=Enter third number: "
if not defined num3 goto endLoop
call :gcd %num1% %num2% %num3%
goto loop
:endLoop
goto :EOF
:gcd
rem Input: a, b, c positive integers
set /A "a = %1, b = %2, c = %3, d = 0, aANDbANDcEVEN = (a&1) + (b&1) + (c&1)"
:while1 a and b are both even do
if %aANDbANDcEVEN% neq 0 goto endwhile1
set /A "a >>= 1, b >>= 1, c >>=1, d += 1, aANDbANDcEVEN = (a&1) + (b&1) + (c&1)"
goto while1
:endwhile1
:while2 a NEQ b do
if %a% equ %b% goto endwhile2
set /A "aIsEven = a&1, bIsEven = b&1"
if %aIsEven% equ 0 ( set /A "a >>= 1"
) else if %bIsEven% equ 0 ( set /A "b >>= 1"
) else if %a% GTR %b% ( set /A "a = (a - b)/2"
) else set /A "b = (b - a)/2"
goto while2
:endwhile2
rem Output: g and d such that g is odd and gcd(a, b) = g×2^d
rem g := a
rem output g, d
set /A "gcd = a * (1<<d)"
echo The GCD is %gcd%
echo/
exit /B
```

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**Batcher****Member**- Registered: 20 Jul 2015
- Posts: 56

...

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**Aacini****Member**- Registered: 05 Dec 2012
- Posts: 116

```
@echo off
setlocal EnableDelayedExpansion
:loop
set "num1="
set /P "num1=Enter first number: "
if not defined num1 goto endLoop
set "num2="
set /P "num2=Enter second number: "
if not defined num2 goto endLoop
set "num3="
set /P "num3=Enter third number: "
if not defined num3 goto endLoop
call :gcd3 %num1% %num2% %num3%
goto loop
:endLoop
goto :EOF
:gcd3
rem Input: a, b, c positive integers
set /A "a = %1, b = %2, c = %3, d = 0, aANDbANDcEVEN = (a&1) + (b&1) + (c&1)"
:while1 a and b and c are all even do
if %aANDbANDcEVEN% neq 0 goto endwhile1
set /A "a >>= 1, b >>= 1, c >>=1, d += 1, aANDbANDcEVEN = (a&1) + (b&1) + (c&1)"
goto while1
:endwhile1
:while2 a NEQ b NEQ c do
if %a% equ %b% if %b% equ %c% goto endwhile2
set /A "aIsEven = a&1, bIsEven = b&1, cIsEven = c&1"
if %aIsEven% equ 0 ( set /A "a >>= 1"
) else if %bIsEven% equ 0 ( set /A "b >>= 1"
) else if %cIsEven% equ 0 ( set /A "c >>= 1"
) else (
if !a! lss !b! set /A t=a, a=b, b=t
if !b! lss !c! set /A t=b, b=c, c=t
if !a! lss !b! set /A t=a, a=b, b=t
set /A "a = (a - c)/2"
)
goto while2
:endwhile2
rem Output: g and d such that g is odd and gcd(a, b, c) = g×2^d
rem g := a
rem output g, d
set /A "gcd = a * (1<<d)"
echo The GCD is %gcd%
echo/
exit /B
```

Antonio

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