golang 随机化快速排序

package main

import (
	"math/rand"
    "fmt"
)

func Partition(A []int, p, r int) int {
	x := A[p]
	i := p

	for j := p + 1; j <= r; j++ {
		if A[j] <= x {
			i++
			A[i], A[j] = A[j], A[i]
		}
	}

	A[p], A[i] = A[i], A[p]
	return i
}

func RandomQuickSort(A []int, p, r int) {
	if p < r {
		q := RandomPartition(A, p, r)
		RandomQuickSort(A, p, q-1)
		RandomQuickSort(A, q+1, r)
	}
}

func RandomPartition(A []int, p, r int) int {
	i := rand.Intn(r - p + 1)
	A[p], A[p+i] = A[p+i], A[p]
	return Partition(A, p, r)
}


func main() {
	//A := []int{3, 6, 9, 9, 8, 4, 2, 1}
	A := []int{9, 8, 7, 6, 5, 4, 3, 2}
	fmt.Println(A)

	RandomQuickSort(A, 0, len(A)-1)
	fmt.Println(A)
}