排序算法复习—归并排序

void mergearray(int a[],int first,int mid,int last,int temp[])
{
    int i=first,j=mid+1;
    int k=0;
    while(i<=mid && j<=last)
    {
        if(a[i] <= a[j])
            temp[k++]=a[i++];
        else
            temp[k++]=a[j++];

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

    while(j<=last)
        temp[k++]=a[j++];

    for(i=0;i<k;i++)
        a[first+i]=temp[i];

}
void mergesort(int a[],int first,int last,int temp[])
{
    if(first<last)
    {
        int mid=(first+last)/2;
        mergesort(a,first,mid,temp);   //使first到mid有序
        mergesort(a,mid+1,last,temp);  //使mid+1到last有序
        mergearray(a,first,mid,last,temp); //合并二个有序数列
        
    }
}
int _tmain(int argc, _TCHAR* argv[])
{
    int a[]={8,22,34,3,14,55,7,43,56,67,31,99};
    int n=sizeof(a)/sizeof(int);
    int *p = new int[n];
    if(p == NULL)
        return -1;
    mergesort(a,0,n-1,p);
    delete[] p;


    for(int k=0;k<n;k++)
    {
        cout<<a[k]<<",";
    }
    int aa;
    cin>>aa;
    return 0;
}