创建链表插入函数，但代码未运行

Question

无法识别在链表类中创建链表插入函数时的错误编译器给出此" error: qualied -id在'('令牌之前的声明中"但似乎所有的括号都放置正确

    #include <iostream>
using namespace std;
    void additem();
    void deleteitem();
    void searchitem(int x);
struct student{
int data;
int * next;
};
   student * head;
   student * curr;
int main()
{
   int x;
   cout << "To add item type 1" << endl;
   cin >> x;
   switch(x)
   {
     case 1:
     additem();
   }
    return 0;
}

void additem()
{
    student * temp;
    if(head == NULL)
    {
        temp = new student;
        head = temp;
        curr = temp;
        temp->next = NULL;
        cout << "Enter data" << endl;
        cin >> temp->data << endl;
    }
    else if(head != NULL)
    {
         temp = new student;
         curr->next = temp;
         curr = temp;
         temp->next = NULL;
         cout << "Enter data" << endl;
         cin >> temp->data ;
    }
    else{
        break;
    }
}

Answer 1

在main中声明一个类和方法。这是不允许的(嵌套函数)。linkedlist::additem需要在main之前定义