Ruby Merge Sort

merge_sort.rb

def merge_sort(ary)
  size = ary.size
  return ary if size <= 1

  mid = size/2

  left, right = ary[0..mid-1], ary[mid..-1]
  left, right = merge_sort(left), merge_sort(right)

  merge(left, right)
end


def merge(left, right)
  result = []
  while left.size > 0 || right.size > 0
    if left.size > 0 && right.size > 0
      result << ((left[0] <= right[0]) ? left.shift : right.shift)
    elsif left.size > 0
      result << left.shift
    elsif right.size > 0
      result << right.shift
    end
  end
  result
end

p merge_sort([*1..100].shuffle) == [*1..100]
p merge_sort([*1..10000].shuffle) == [*1..10000]