CommDenom.rb

=begin

Common denominators

You will have a list of rationals in the form

 { {numer_1, denom_1} , ... {numer_n, denom_n} }
or

 [ [numer_1, denom_1] , ... [numer_n, denom_n] ]
or

 [ (numer_1, denom_1) , ... (numer_n, denom_n) ]
where all numbers are positive ints.

You have to produce a result in the form

 (N_1, D) ... (N_n, D)
or

 [ [N_1, D] ... [N_n, D] ]
or

 [ (N_1', D) , ... (N_n, D) ]
or

{{N_1, D} ... {N_n, D}}
depending on the language (See Example tests)

in which D is as small as possible and

 N_1/D == numer_1/denom_1 ... N_n/D == numer_n,/denom_n.
Example:

convertFracs [(1, 2), (1, 3), (1, 4)] `shouldBe` [(6, 12), (4, 12), (3, 12)]

=end

# My Solution
def convertFracts(lst)
  cm = 1
  lst.each_with_index do |x,i|
    cm = cm.lcm(lst[i][1])
  end
  lst.each_with_index do |x, i|
    lst[i][0] = cm/(lst[i][1])*(lst[i][0])
    lst[i][1] = cm
  end
  lst
end

# Better Solution
def convertFracts(lst)
  lcm = lst.reduce(1) { |x,y| x.lcm(y[1]) }
  lst.map { |x| [lcm/x[1]*x[0], lcm] }
end