快速排序

quick_sort.rb

def quick_sort(arr)
  len = arr.length
  
  return arr if len == 1
  
  old_index = 0
  x = arr[old_index]

  if len == 2
    if arr[1] < x
      arr[0] = arr[1]
      arr[1] = x
    end
  end

  i = 1
  j = len - 1

  while j > i
    if arr[j].to_i < x
      arr[old_index] = arr[j]
      arr[j] = x
      old_index = j

      while i < j
        if arr[i].to_i > x
          arr[old_index] = arr[i]
          arr[i] = x
          old_index = i

          break
        end
        i = i + 1
      end
    end

    j = j - 1
  end

  sub_arr1 = quick_sort(arr[0..old_index])
  sub_arr2 =  quick_sort(arr[old_index+1..len-1])
  arr = sub_arr1.concat(sub_arr2)
  return arr
end

arr = [49,38,65,97,76,13,27,50]
quick_sort(arr)