归并排序程序

void merge(int *a,int p,int q,int r)//将两段子数组排进一个临时数组
{
int beg1,end1,beg2,end2;
beg1 = p;   end1 = q;
beg2 = q+1; end2 = r;
int *t = (int*)malloc((r-p+1)*sizeof(int));
int k = 0;
while((beg1 <= end1) && (beg2 <= end2))//比较小的放进去
{
if(a[beg1] < a[beg2])
{
t[k] = a[beg1++];
k++;
}
else
{
t[k] = a[beg2++];
k++;
}
}
while(beg1 <= end1)//剩余的直接放在后面
{
t[k] = a[beg1];
k++;
beg1++;
}
while(beg2 <= end2)
{
t[k] = a[beg2];
k++;
beg2++;
}
int m = 0;
for(int i = p;i <= r;i++)
{
a[i] = t[m];
m++;
}
free(t);
}
void guibing(int *a,int first,int last)
{
int mid = 0;
if(first < last)//必须是小于不能等于，否则死循环
{
mid = (first + last)/2;
guibing(a,first,mid);
guibing(a,mid+1,last);
        merge(a,first,mid,last);
}
}