以下代码经测试，排序5000000（五千万）int型数据没有问题！

第一个参数是数组首地址
第二个参数是数组元素个数
void MergeSort(int * const arr, const DWORD number)//归并排序
{
DWORD i;
DWORD index1, index2;//将数组分为两个，分别作为两个数组第一个元素的下标
DWORD tmpIndex1, tmpIndex2;//分别指向两个数组中的元素相对于index1、index2的步进
DWORD step;//步进
int *tmpArr = NULL;
if (number < 2)
{
return;
}
tmpArr = (int *)malloc(number*sizeof (int));
if (NULL == tmpArr)
{
printf("分配缓存出错！\n");
getch();
return;
}
for (step=1; step {
index1 = 0;
index2 = index1 + step;
tmpIndex1 = 0;
tmpIndex2 = 0;
i = 0;
while ((index2+tmpIndex2) < number)
{
while ((tmpIndex1 < step) && (tmpIndex2 < step) && ((index2+tmpIndex2) < number))
{
if (arr[index1+tmpIndex1] <= arr[index2+tmpIndex2])
{
tmpArr[i] = arr[index1+tmpIndex1];
tmpIndex1++;
}
else
{
tmpArr[i] = arr[index2+tmpIndex2];
tmpIndex2++;
}
i++;
}
while (tmpIndex1 {
tmpArr[i++] = arr[index1+tmpIndex1];
tmpIndex1++;
}
while ((tmpIndex2 {
tmpArr[i++] = arr[index2+tmpIndex2];
tmpIndex2++;
}
index1 = index1 + 2*step;
index2 = index2 + 2*step;
tmpIndex1 = 0;
tmpIndex2 = 0;
}
memcpy(arr, tmpArr, number*sizeof (int));
}
free(tmpArr);
}
void MergeSort(int * const arr, const DWORD number)//归并排序
{
DWORD i;
DWORD index1, index2;//将数组分为两个，分别作为两个数组第一个元素的下标
DWORD tmpIndex1, tmpIndex2;//分别指向两个数组中的元素相对于index1、index2的步进
DWORD step;//步进
int *tmpArr = NULL;
if (number < 2)
{
return;
}
tmpArr = (int *)malloc(number*sizeof (int));
if (NULL == tmpArr)
{
printf("分配缓存出错！\n");
getch();
return;
}
for (step=1; step {
index1 = 0;
index2 = index1 + step;
tmpIndex1 = 0;
tmpIndex2 = 0;
i = 0;
while ((index2+tmpIndex2) < number)
{
while ((tmpIndex1 < step) && (tmpIndex2 < step) && ((index2+tmpIndex2) < number))
{
if (arr[index1+tmpIndex1] <= arr[index2+tmpIndex2])
{
tmpArr[i] = arr[index1+tmpIndex1];
tmpIndex1++;
}
else
{
tmpArr[i] = arr[index2+tmpIndex2];
tmpIndex2++;
}
i++;
}
while (tmpIndex1 {
tmpArr[i++] = arr[index1+tmpIndex1];
tmpIndex1++;
}
while ((tmpIndex2 {
tmpArr[i++] = arr[index2+tmpIndex2];
tmpIndex2++;
}
index1 = index1 + 2*step;
index2 = index2 + 2*step;
tmpIndex1 = 0;
tmpIndex2 = 0;
}
memcpy(arr, tmpArr, number*sizeof (int));
}
free(tmpArr);
}

测试代码：