quicksort.rb

def quicksort(a)
  return a unless a.count > 1
  pivot = a[0]
  less = a.select {|num| num < pivot }
  equal = a.select {|num| num == pivot }
  greater = a.select {|num| num > pivot }
  
  return quicksort(less) + equal + quicksort(greater)
end