算法回鍋肉——快速排序（隨機）

示例代碼純粹是爲了加深印象，選擇的目標語言有更便捷的實現方式，另外去掉了一些假設條件檢查。

#encoding:gbk

Size = 20
arr = Array.new(Size) do	#初始化待排序數組，隨機填寫元素
	rand(Size)
end

def random_partition(a,p,r) #隨機選擇主元素，抗拼爹
	i = rand(r - p) + p
	a[r],a[i] = a[i],a[r]
	partition(a,p,r)
end

def partition(a,p,r) #分片，粗糙拆分爲兩類
	x = a[r]
	i = p - 1
	for j in p..r - 1
		if a[j] < x
			i += 1
			a[i],a[j] = a[j],a[i]
		end
	end
	i += 1
	a[i],a[r] = a[r],a[i]
	i
end

def quick_sort(a,p,r)
	if p < r
		q = random_partition(a,p,r)
		quick_sort(a,p,q - 1) #遞歸快速排序
		quick_sort(a,q + 1,r)
	end
end

puts arr.inspect
arrc = arr.clone
quick_sort(arrc,0,arrc.size - 1)
puts arrc.inspect

輸出如下：

---------- Ruby ----------
[3, 15, 12, 1, 0, 16, 6, 15, 10, 13, 0, 18, 18, 15, 8, 15, 14, 8, 12, 15]
[0, 0, 1, 3, 6, 8, 8, 10, 12, 12, 13, 14, 15, 15, 15, 15, 15, 16, 18, 18]

Output completed (1 sec consumed) - Normal Termination