新人求助！记录程序时间出错

#include
#include
#include
#include"sort.h"
using namespace std;
int main()
{
int choice, n, i, j;
DWORD start, end;
while(1)
{
cout << "输入数据的方式：" << endl;
cout << "1、手动输入" << endl;
cout << "2、系统自动产生" << endl;
cout << "输入方式序号：" << endl;
cin >> choice;

    if (choice == 1)
    {
        cout << "排序的元素个数：" << endl;
        cin >> n;
        int *a = new int[n];
        int *b = new int[n];
        int *temp = new int[n];
        cout << "要排序的元素：" << endl;

        for (i = 0; i < n; i++)
        {
            cin >> a[i];
            b[i] = a[i];
        }

        cout << "快排结果：" << endl;
        Quicksort(a, 0, n - 1);

        for (i = 0; i < n; i++)
            cout << a[i] << " ";

        cout << endl;
        cout << "归并结果：" << endl;
        Mergesort(b, 0, n - 1);

        for (i = 0; i < n; i++)
            cout << b[i] << " ";

        cout << endl;
    }

    else if (choice == 2)
    {
        cout << "下面将随机产生10组数据：" << endl;
        for (i = 1; i <= 10; i++)
        {   
            cout << "#" << i << endl;
            int *a = new int[10000 * i];
            int *b = new int[10000 * i];
            int *temp = new int[10000 * i ];

            for (j = 0; j < 10000 * i; j++)
            {
                a[j] = rand() % 100000;
                b[j] = a[j];
            }

            start = GetTickCount();
            Quicksort(a, 0, 10000 * i - 1);
            end = GetTickCount();
            cout << "快速排时间：" << end - start << "ms" << endl;
            start = GetTickCount();
            Mergesort(b, 0, 10000 * i - 1);
            end = GetTickCount();
            cout << "归并排时间：" << end - start << "ms" << endl;
        }
    }
    else
        break;
}
system("pause");
return 0;

程序中choice==1是用来测试两个排序算法有没有正确排序的，经测没问题，可是到随机生成后就有问题了，输出的时间很不对劲...


另外，别人的程序在自己电脑上没问题，到我的电脑就出现同样问题了！！！！！

图片补在下面

计算机的时间精度也就是几十ms级别。你的数据量太小了。把数据扩大100倍。

你申请了内存之后要释放的啊，你这样每申请一次都会有内存泄露，不应该是关掉重启出错，理论上运行时间久点，最后a，b会没有内存申请返回NULL，时间就不可预知了，所以排序时间会变得混乱，你在 for (i = 1; i <= 10; i++)这个循环的末尾加上delete []a； delete[]b；如下：
for (i = 1; i <= 10; i++)
{

cout << "#" << i << endl;
int *a = new int[10000 * i];
int *b = new int[10000 * i];
int *temp = new int[10000 * i ];

        for (j = 0; j < 10000 * i; j++)
        {
            a[j] = rand() % 100000;
            b[j] = a[j];
        }

        start = GetTickCount();
        Quicksort(a, 0, 10000 * i - 1);
        end = GetTickCount();
        cout << "快速排时间：" << end - start << "ms" << endl;
        start = GetTickCount();
        Mergesort(b, 0, 10000 * i - 1);
        end = GetTickCount();
        cout << "归并排时间：" << end - start << "ms" << endl;
                    delete []a;
                    delete []b;
    }