This problem was asked by Amazon. Given n numbers, find the greatest common denominator between them. For example, given the numbers [42, 56, 14], return 14.

184.rb

def gcd a, b
    return a if b == 0
    return gcd(b, a % b)
end  

def gcd_in_list list 
    list = list.sort
    grt = 0
    list.each do |i|
        grt = gcd(i, grt)
    end 
    puts grt
end

list = [ 42, 56, 14]

puts gcd_in_list list