归并排序怎么拆开成小的板块

请问归并排序怎么拆开成小的板块？归并程序我已经做出来了
void merge(int num[],int left,int right,int end)     //归并
{
    int r[10];
    int i=left;
    int j=right;
    for(int i=left;i<=end;i++)
        r[i]=num[i];
    for(int i=left;i<=end;i++)
        num[i]=0;
    while(i<right&&j<=end)
    {
        if(r[i]<=r[j])
        {
            num[i]=r[i];
            num[j]=r[j];
            i++;
            j++;
        }
        else
        {
            num[i]=r[j];
            num[j]=r[i];
            i++;
            j++;
        }
    }
    if(j<end)
        for(int k=j+1;k<=end;k++)
            num[k]=r[k];
}