快速排序

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <stack>
using namespace std;
void quicksort(int* a, int from, int to);
void quicksort(int* a, int length);
void quicksort_nonrecursive(int* a, int from, int to);
int partition(int* a, int from, int to);

void quicksort(int* a, int from, int to)
{
    if (from<to)
    {
        int pivot = partition(a, from, to);
        quicksort(a, from, pivot-1);
        quicksort(a, pivot+1, to);
    }
}

void quicksort(int* a, int length)
{
    return quicksort(a,0,length-1);
}

int partition(int* a, int from, int to)
{
    int x = a[to];
    int i = from-1;
    for(int j = from; j<=to-1; ++j) {
        if (a[j]<=x)
        {
            ++i;
            swap(a[i],a[j]);
        }
    }
    swap(a[i+1],a[to]);
    return i+1;
}

int main()
{
    int i[9] = {3, 0, 6, 6, 7, 4, 6, 9, 8};
    quicksort(i,9);
    for(int j = 0; j<9; j++)
    {
        printf("%d\t",i[j]);
    }
}