Rubyでのクイックソート

quick_sort.rb

def quicksort(seq)
  return seq if seq.size.zero?
  
  pivot = seq.shift
  right = []
  left = []
  seq.each{|e|
    if e <= pivot
      left.push(e)
    else
      right.push(e)
    end
  }
  
  quicksort(left) + [pivot] + quicksort(right)
end

arr = [1,53,36,77,22,100,4,20]
p(quicksort(arr))