头指针head存在问题，最后链表出现单节点循环情况，找不到问题

预期是输出1 2 3 4。但结果为一个奇怪的数不停循环。

```c++

#include<iostream>
using namespace std;
class A
{
public:
    A* next;
    int data;
    A()
    {
        data = 0;
        next= NULL;
    }
};
class B
{
public:
    A* head;
    void init()
    {
        head = new A();
    }
    void add(A a)
    {
        A* point = head;
        while (point->next != NULL)
        {
            point = point->next;
        }
        point->next = &a;
    }
};
class C
{
public:
    void cb(B b)
    {
        for (int i = 0; i < 4; i++)
        {
            A a = A();
            a.data = i+1;
            b.add(a);
        }
    }
};
int main()
{
    B b;
    b.init();
    C c;
    c.cb(b);
    A* point = b.head;
    while ((point->next)!=NULL)
    {
        cout << point->next->data << endl;
    }
}

如果帮助到你，请采纳，谢谢！

 

 
#include<iostream>
using namespace std;
class A
{
public:
    A* next;
    int data;
    A()
    {
        data = 0;
        next= NULL;
    }
};
class B
{
public:
    A* head;
    void init()
    {
        head = new A();
    }
    void add(A* a)
    {
        A* point = head;
        while (point->next != NULL)
        {
            point = point->next;
        }
        point->next = a;
    }
};
class C
{
public:
    void cb(B& b)
    {
        for (int i = 0; i < 4; i++)
        {
            A* a = new A();
            a->data = i+1;
            b.add(a);
        }
    }
};
int main()
{
    B b;
    b.init();
    C c;
    c.cb(b);
    A* point = b.head;
    while ((point->next)!=NULL)
    {
        cout << point->next->data << endl;
        point = point->next;
    }
}