In doubly linked list we have two portion reserved for addresses one for the next address and other for the previous address.

Doubly linked list hold the reference for both the list either previous to it or next to it and the middle portion contains the data for the node.

Basic Operations

• Insertion − add element at beginning of the list.

• Deletion − delete an element from the beginning of the list.

• Insert Last − add an element in the end of the list.

• Delete Last − delete an element from the end of the list.

• Insert After − add an element after an item of the list.

• Delete − delete an element from the list .

• Display forward − displaying complete list in going forward.

• Display backward − displaying complete list in going backward.

Insertion in Doubly Linked List

//insert link at the first location
void insertFirst(int key, int data) {

   //create a link
   struct node *link = (struct node*) malloc(sizeof(struct node));
   link->key = key;
   link->data = data;
	
   if(isEmpty()) {
      //make it the last link
      last = link;
   }else {
      //update first prev link
      head->prev = link;
   }

   //point it to old first link
   link->next = head;
	
   //point first to new first link
   head = link;
}

Deletion in Doubly Linked List

While deletion just free the previous position by giving its position to the previous node and the next position to another if it exists otherwise set NULL for both

//delete first item
struct node* deleteFirst() {

   //save reference to first link
   struct node *tempLink = head;
	
   //if only one link
   if(head->next == NULL) {
      last = NULL;
   }else {
      head->next->prev = NULL;
   }
	
   head = head->next;
	
   //return the deleted link
   return tempLink;
}