Question

I have a simple question in understanding the pointers and struct definitions in the linked list code.

1)

typedef struct node
{
 struct node* next;
 int val;

}node;

here if I use two “node” when i initialize node *head; which node I am referring to?

2) Here I use an int val in the struct. If I use a void* instead of int is there any thing thats going to change ?

3)Also if I pass to a function

reverse(node* head)
{
    node* temp = head; or node* temp = *head;     
    //what is the difference between the two
}

I am sorry if these are silly question I am new to c language.

Thanks & Regards,
Brett

Answer 1

<1>
in C you need to specify struct node for structs

    struct node 
    {
...
    } node;

the last ‘node’ is variable of type struct node
e.g.

node.val = 1;

and not a type.

if you want to use ‘node’ as a type you need to write

typedef struct node { .. } node;

<2>
if you use void* you will need a mechanism to handle what the pointers point to e.g. if void* points to an integer you need keep the integer either on the stack or the heap.

node n;
int value = 1;
n.val = &value; // pointing to a single integer on stack

int values[]={1,2,3};
n.val = values; // pointing to an array of integers on stack

void* ptr = malloc(sizeof(int));
n.val = ptr;  // pointing to a single (uninit) integer allocated on heap
int* ptrval = (int*)ptr; // setting an int ptr to the same memory loc.
*ptrval = value; // ptrval now points to same as n.val does

<3>
reverse(node* head)
head is a pointer to your list, *head is the content of what the pointer points to (first node below)

head->[node next]->[node next]->[node
next]

EDIT: rephrased and edited.
EDITx2: apparently the question got edited and a typedef was added so the question was altered.