Random_QuickSort

#include "stdafx.h"

int PARTITION(int a[], int p, int r)                                           //以遞增順序排序
{
    int x = a[r];
    int i = p - 1;
    for (int j = p; j < r; ++j)
    {
        if (a[j] < x)
        {
            ++i;
            int temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }
    }
    int temp = a[i + 1];
    a[i + 1] = a[r];
    a[r] = temp;
    return i + 1;
}

int Random_Partition(int a[], int p, int r)
{
    srand(time(NULL));                                            //以當前時間作爲種子，以便每次產生的隨機數不同
    int i = rand() % (r - p) + p;                                 //產生隨機數
    int temp = a[i];
    a[i] = a[r];
    a[r] = temp;
    return PARTITION(a, p, r);
}

void Random_QuickSort(int a[], int p, int r)
{
    if (p < r)
    {
        int q = Random_Partition(a, p, r);
        Random_QuickSort(a, p, q - 1);
        Random_QuickSort(a, q + 1, r);
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    int a[] = { 3, 1, 7, 5, 9, 4, 12, 0 };
    int len = sizeof(a) / 4 - 1;
    Random_QuickSort(a, 0, len);
    for (int i = 0; i < len + 1; ++i)
    {
        cout << a[i] << endl;
    }
    return 0;
}