排序：归并

#include <stdio.h>

// 交换函数
void swap (int a[], int i, int j)
{
int tmp = a[i];
a[i] = a[j];
a[j] = tmp;
}

// 打印数组
void printA (int *a, int len)
{
int i;
for (i = 0; i < len; i++)
{
printf ("%4d", a[i]);
}

printf ("\n");
}

// a 是数组  tmp  是缓冲区
void merge(int *a, int left, int mid, int right, int *tmp)
{
int i = left;
int j = mid + 1;
int k = 0;

while (i <= mid && j <= right)
{
if (a[i] > a[j])
tmp[k++] = a[j++];
else
tmp[k++] = a[i++];
}

while (i <= mid)
tmp[k++] = a[i++];

while (j <= right)
tmp[k++] = a[j++];

k = 0;
for (i = left; i <= right; i++)
{
a[i] = tmp[k++];
}
}

void mergeSort(int *a, int left, int right, int *tmp)
{
if (left >= right)
return;

int mid = (left + right)/2;
mergeSort (a, left, mid, tmp);    // 对左边部分进行归并排序
mergeSort (a, mid+1, right, tmp); // 对右边部分进行归并排序
merge (a, left, mid, right, tmp); // 将两部分数据进行归并
}

int main()
{
int a[10] = {9,6,8,0,3,1,2,4,7,5};
int len = sizeof(a) / sizeof(a[0]);
int tmp[10];
mergeSort (a, 0, len-1, tmp);
printA (a, len);

return 0;
}