Delete a node in a Doubly Linked List - Dieptranivsr/DroneIVSR GitHub Wiki

// C++ program to delete a node from
// Doubly Linked List
#include <bits/stdc++.h>
using namespace std;

/* a node of the doubly linked list */
class Node
{
	public:
	int data;
	Node* next;
	Node* prev;
};

/* Function to delete a node in a Doubly Linked List.
head_ref --> pointer to head node pointer.
del --> pointer to node to be deleted. */
void deleteNode(Node** head_ref, Node* del)
{
	/* base case */
	if (*head_ref == NULL || del == NULL)
		return;

	/* If node to be deleted is head node */
	if (*head_ref == del)
		*head_ref = del->next;

	/* Change next only if node to be
	deleted is NOT the last node */
	if (del->next != NULL)
		del->next->prev = del->prev;

	/* Change prev only if node to be
	deleted is NOT the first node */
	if (del->prev != NULL)
		del->prev->next = del->next;

	/* Finally, free the memory occupied by del*/
	free(del);
	return;
}

/* UTILITY FUNCTIONS */
/* Function to insert a node at the
beginning of the Doubly Linked List */
void push(Node** head_ref, int new_data)
{
	/* allocate node */
	Node* new_node = new Node();

	/* put in the data */
	new_node->data = new_data;

	/* since we are adding at the beginning,
	prev is always NULL */
	new_node->prev = NULL;

	/* link the old list off the new node */
	new_node->next = (*head_ref);

	/* change prev of head node to new node */
	if ((*head_ref) != NULL)
		(*head_ref)->prev = new_node;

	/* move the head to point to the new node */
	(*head_ref) = new_node;
}

/* Function to print nodes in a given doubly linked list
This function is same as printList() of singly linked list */
void printList(Node* node)
{
	while (node != NULL)
	{
		cout << node->data << " ";
		node = node->next;
	}
}

/* Driver code*/
int main()
{
	/* Start with the empty list */
	Node* head = NULL;

	/* Let us create the doubly linked list 10<->8<->4<->2 */
	push(&head, 2);
	push(&head, 4);
	push(&head, 8);
	push(&head, 10);

	cout << "Original Linked list ";
	printList(head);

	/* delete nodes from the doubly linked list */
	deleteNode(&head, head); /*delete first node*/
	deleteNode(&head, head->next); /*delete middle node*/
	deleteNode(&head, head->next); /*delete last node*/

	/* Modified linked list will be NULL<-8->NULL */
	cout << "\nModified Linked list ";
	printList(head);

	return 0;
}