Question

i am trying to make a model-class to find the grates common division for 2 numbers. if i put 68 and 22 the answer is 2 and is correct but if i put 678 352 the results is 326 and is wrong! should be 2! any ideas??

def gcd 
  if firstnumber > secondnumber
    div= firstnumber/ secondnumber
    ip=firstnumber % secondnumber
    fi = div / ip
    ip
  else 
    i = firstnumber 
    s = secondnumber 
    secondnumber = firstnumber 
    firstnumber = s 
    div= firstnumber/ secondnumber 
    ip=firstnumber % secondnumber 
    fi = div / ip ip 
  end 
end

with loop

def gcd
   a = firstnumber
   b=secondnumber
   ip = 50
   if firstnumber > secondnumber
     begin   
       fi=a/b
       re=a%b    
       fi=b/re
       re=re%b
       ip=re        
     end until ip != 0
     return re  
   end
   else
     i = firstnumber
     s = secondnumber
     secondnumber = firstnumber
     firstnumber = s
     div= firstnumber/ secondnumber
     ip=firstnumber % secondnumber
     fi = div / ip
     ip
   end
end

$end

and the same thing happens

Answer 1

Ruby has a Class Integer which has the method gcd. Don’t reinvent the wheel. Read here http://www.ruby-doc.org/core-1.9.3/Integer.html#method-i-gcd

irb(main):001:0> 68.gcd(22)
=> 2
irb(main):002:0> 678.gcd(352)
=> 2

The source for that method is

   def gcd(n)
     m = self.abs
     n = n.abs

     return n if m == 0
     return m if n == 0

     b = 0
     while n[0] == 0 && m[0] == 0
       b += 1; n >>= 1; m >>= 1
     end
     m >>= 1 while m[0] == 0
     n >>= 1 while n[0] == 0
     while m != n
       m, n = n, m if n > m
       m -= n; m >>= 1 while m[0] == 0
     end
     m << b
   end