array = [72,6,57,88,60,42,83,73,48,85] def quick_sort(a) (x=a.pop) ? quick_sort(a.select{|i| i <= x}) + [x] + quick_sort(a.select{|i| i > x}) : [] end p quick_sort(array) ==》[6, 42, 48, 57, 60, 72, 73, 83, 85, 88]