CODEWITHSUNDEEP
c++listpointersdoubly-linked-list
user7065138
user7065138

Reputation:

Difference between pointer to node and node as whole object?

If I have structure: /* Linked list structure */

struct list 
{
   struct list *prev;
   int data;
   struct list *next;
} ** *node = NULL, *first = NULL, *last = NULL, *node1 = NULL, *node2 = NULL**;

class linkedlist {
public: 

    /* Function for create/insert node at the beginning of Linked list */
    void insert_beginning() {
        **list *addBeg = new list;**
        cout << "Enter value for the node:" << endl;
        cin >> addBeg->data;
        if(first == NULL) {
            addBeg->prev = NULL;
            addBeg->next = NULL;
            first = addBeg;
            last = addBeg;
            cout << "Linked list Created!" << endl;
        }
        else {
            addBeg->prev = NULL;
            first->prev = addBeg;
            addBeg->next = first;
            first = addBeg;
            cout << "Data Inserted at the beginning of the Linked list!" << endl;
        }
    }

What is the SYNTAX difference between creating a new node (with 2 pointers and data) and just a single pointer apart from node, to use in same program. (Difference between bolded parts)

Upvotes: 1

Views: 9183

Answers (1)

Thomas Matthews
Thomas Matthews

Reputation: 57678

Here are some examples.

Declaring a node variable 

node n;

Here n is a variable or instance of type node.

Declaring a pointer to node type

node * pointer_to_node;

Notice the * after the type identifier. The * is used to declare pointers.

Also notice that the pointer is not pointing to anything.

Pointing the Pointer
A pointer can point to anything of its type. So the following is valid: 

node n;
node * pointer_to_node = &n;

In the above example, the pointer_to_node is initialized to point to the variable n. 

node * pointer_to_dynamic = new node;

In the above statement, the program allocates a node instance in dynamic memory. The location of the memory is assigned to the pointer_to_dynamic variable. In other words, the variable pointer_to_dynamic now points to the newly allocated dynamic memory.

Upvotes: 2

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