如何将链表与不同的结构链接起来

Question

I have 2 different stuct

    typedef struct name {

    char*markerName;
    struct test *next;

}name_t;

 typedef struct test {

    int grade;
    int studentNumber;
    struct test *next;


}test_t;

and this function

void test(name_t* marker1,int data)
{
        test_t *temp= malloc(sizeof(test_t));
        test_t *location=NULL;
        temp->grade=data;
        temp->next=NULL;
        location=marker1->next;
        if(location==NULL)
        {
        //  printf("%i \n",temp->grade);
            marker1->next=temp;
        }
        else
        {
            while(location!=NULL)
            {
                printf("%i \n",location->grade);
                printf("%p \n",location->next);
                location=location->next;
            }
            location=temp;
        }
}

the problem is we are creating an array of the stuct name and creating a linked list of the test after EACH ELEMENT OF THE ARRAY. How would I link the node of the struct name into the stuct test?

I printed the next out and they keep pointing to NULL pointer.

Answer 1

You are overshooting past the end of your linked list. You end up with 'NULL' for your location variable, which, even if it could be assigned, is still a local variable that goes out of context when your function exits. Your while loop should look more like this:

while(location->next != NULL)
{
    printf("%i \n",location->grade);
    printf("%p \n",location->next);
    location = location->next;
}

location->next = temp;

Answer 2

Strictly speaking, a linked list can only contain one data type. If you want to have a list containing both structure types, you can emulate this using a union:

struct name {
   char* markerName;
};

struct test {
   int grade;
   int studentNumber;
};

// Indicates the type of data stored in the union
enum dtype { NONE, NAME, TEST };

// Combination of the above structures, suitable for a mixed-type list
struct combo {
   struct combo*   next; // Next structure in the linked list
   enum dtype      type; // Indicates which of the union fields is valid
   union {
      struct name  name;
      struct test  test;
   };
};

This stores both sets of data in a single structure, allows you to make lists from the structures, and enables you to keep track of which type of data is currently valid.

Answer 3

You could use a pointer to type void . This, of course, assumes that you know the type of the next object somehow.

When you want to create a heterogeneous data structure, it might be smarter to have only one struct type of nodes, and have two "payload" variables in the nodes, one which tells you the type of the node, and a pointer to a structure with the actual data.

Answer 4

What about a struct with two types of next pointers: one of type name_t and other of type test_t. You can use the one you want for linking and leave the other one NULL. I hope I understood your question correctly.