程序代码：

void combine(node *head1, node *head2)  //合并
{
    node *p1, *p2, *pre1 = NULL, *pre2 = NULL;  //pre指向前驱结点
    if (!head1 && !head2)
    {
        puts("两个电话本都是空的，合不了");
    }
    else
    {
        p1 = head1;
        p2 = head2;
        while (p1)
        {
            while (p2)
            {
                while ((strcmp(p2->item.name,p1->item.name) != 0) || (p2->item.number != p1->item.number))
                {
                    pre2 = p2;
                    p2 = p2->next;
                }
                if (p2->next)
                {
                    if (!pre2)
                    {
                        p2 = p2->next;
                        head2 = head2->next;
                    }
                    else
                    {
                        pre2->next = p2->next;
                    }
                }
                else
                {
                    p2 = head2;
                }
            }
            p2 = head2;
            pre1 = p1;
            p1 = p1->next;
        }
        pre1->next = head2;
        p1 = head1;
        display(p1);  //打印
    }
}