Ruby Implementation of Quick Sort

quick_sort.rb

def quick_sort(array)
  return array if array.size <= 1
  
  # select a pivot element
  # here we get the first element of the array
  pivot ||= array.shift
  
  #use the pivot to break down the array into 2 subarray(left and right)
  left = array.select { |n| n < pivot }
  right = array.select { |n| n >= pivot }
  
  # recursively call quick_sort with the left and right array
  # then pick a pivot
  # if pivot is larger than the value to the right
  # switch their positions. 
  return [*quick_sort(left), pivot, *quick_sort(right)]
end