不兼容的指针类型结构节点到节点

Question

I'm doing a lab for my course and I'm having an issue with some warnings. We are given a struct that we cannot change:

typedef struct Element{
    int value;
    double key1;
    double key2;
    struct NODE* next;
    struct NODE* sort1;
    struct NODE* sort2;
}Node;

And this is the main code:

struct Element * randomizer(int A){
     /*Function to have "real" random*/

    srand((unsigned int) time(0));

     Node *head;
     Node *ptr;
    int i = 0;

    head = NULL;
    ptr = NULL;



    /*Vlaues beiong intialized*/
    for ( i = 0 ; i <= A; i++){
    ptr = malloc(sizeof(Node));
        ptr->value = rand()%11;
        while (ptr->value == 0 || ptr->value == 10 ){
            ptr->value = rand()%11;
        }
    ptr->key1 =  (rand()%41)+10;

        while (ptr->value == 10.0 || ptr->value == 50.0 ){
              ptr->key1 =  (rand()%41)+10;
        }
    ptr->key2 = (rand()%41)+50;

        while (ptr->value == 50.0 || ptr->value == 90.0 ){
                     ptr->key2 =  (rand()%41)+50;
               }

    ptr->next = head;

    head = ptr;
    }

    ptr->sort1 = NULL;
    ptr->sort2 = NULL;

    return ptr;
}

At ptr->next = head; I get an error saying

incompatible pointer types assigning type node to struct node

How can I do this correctly?

Answer 1

head is declared as Node * , and because of the typedef this is equivalent to struct Element* .

The next member is declared as struct NODE * .

struct NODE * is not the same as struct Element * .

You probably should change the struct member to

struct Element *next;

Answer 2

C is case-sensitive, so Node and NODE are two different, unrelated things. You're trying to use Node in your code, but the declaration you say you can't change has NODE , so they are incompatible. You probably need to change your code to also use NODE .

Answer 3

In this typedef declaration

typedef struct Element{
    int value;
    double key1;
    double key2;
    struct NODE* next;
    struct NODE* sort1;
    struct NODE* sort2;
}Node;

You declared two different structures. The first one has the type struct Element with the type alias Node and within its definition you declared the type struct NODE .

Even if there was not a typo and the data members have the type struct Node * instead of struct NODE * nevertheless the types struct Node and Node are not the same types.

You should declare the structure like

typedef struct Element{
    int value;
    double key1;
    double key2;
    struct Element* next;
    struct Element* sort1;
    struct Element* sort2;
}Node;