Free doubly linked list C

A Doubly linked list is used in navigation systems or to represent a classic deck of cards. A Doubly linked list is a bidirectional linked list; i.e., you can traverse it from head to tail node or tail to head node. Unlike singly-linked lists, its node has an extra pointer that points at the last node.

How Do You Implement a Doubly Linked List?

You create nodes of doubly-linked lists using classes or structures. These nodes are then linked with each other using the next and the previous pointer.

Code:

//A c++ program to implement linked list

#include

using namespace std;

/* A class to create node */

class Node

{

public:

int data;

Node *next;

Node *prev;

};

//A function to insert at the

//beginning of the list

void push[Node** head, int newdata]

{

//create new node

Node* newnode = new Node[];

/* put in the data */

newnode->data = newdata;

/* As we are adding at the beginning,

prev is always NULL */

newnode->prev = NULL;

/* link new node's next to head */

newnode->next = [*head];

/* change prev of head node to newnode */

if[[*head] != NULL]

[*head]->prev = newnode ;

/* changing head node */

[*head] = newnode;

}

/* A c++ program to print the list */

void printlist[Node *head]

{

while[head != NULL]

{

cout data next;

}

}

int main[]

{

/* We will start with an empty list */

Node* head = NULL;

/*lets create a linked list: 2->3->5->7 */

push[&head, 7];

push[&head, 5];

push[&head, 3];

push[&head, 2];

cout prev = NULL;

/* link the next of newnode to the head */

newnode->next = [*head];

/* change prev of head node to newnode */

if[[*head] != NULL]

[*head]->prev = newnode ;

/* changing head */

[*head] = newnode;

}

/* A c++ program to traverse the linked list */

void traverse[Node *node]

{

while[node != NULL]

{

cout data next;

}

}

/* Function to reverse traverse a Linked List */

void revtraverse[Node **head]

{

Node* tail = *head;

// Traversing till tail of the linked list

while [tail->next != NULL] {

tail = tail->next;

}

// Traversing linked list from tail

// and printing the node->data

while [tail != *head] {

cout data prev;

}

cout data 3->5->7 */

push[&head, 7];

push[&head, 5];

push[&head, 3];

push[&head, 2];

cout prev = newnode;

/* changing head */

[*head] = newnode;

}

/* A function to insert a node after a given node */

void insertAfter[Node* prevnode, int newdata]

{

/*1. check if the given prevnode is NULL */

if [prevnode == NULL]

{

coutnext = prevnode->next;

/* 5. Make the prevnode's next as newnode */

prevnode->next = newnode;

/* 6. Make prevnode as newnode's prev */

newnode->prev = prevnode;

/* 7. Change previous of newnode's next node */

if [newnode->next != NULL]

newnode->next->prev = newnode;

}

/* A function to insert at the end of the list */

void append[Node** head, int newdata]

{

/* create newnode */

Node* newnode = new Node[];

Node* last = *head;

/* put in the data */

newnode->data = newdata;

/*This newnode is going to be the last node, so

we will make next of it as NULL*/

newnode->next = NULL;

/* check if the Linked List is empty, then make the new

node as head */

if [*head == NULL]

{

newnode->prev = NULL;

*head = newnode;

return;

}

/* Else traverse till the last node */

while [last->next != NULL]

last = last->next;

/* Change the next of last node */

last->next = newnode;

/* Make last node as new node's prev */

newnode->prev = last;

return;

}

// A function to print the list

void printList[Node* node]

{

while [node != NULL]

{

cout7->6->NULL

// Insert 4 at the end

append[&head, 4]; //1->7->6->4->NULL

// Insert 8, after 7

insertAfter[head->next, 8]; //1->7->8->6->4->NULL

cout 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;

}

/* A function to insert a node at the beginning of the list*/

void push[Node** head, int newdata]

{

/* create newnode */

Node* newnode = new Node[];

/* put in the data */

newnode->data = newdata;

/* link the new node's next to head

and previous as NULL */

newnode->next = [*head];

newnode->prev = NULL;

/* link the head node's prev to new node */

if [[*head] != NULL]

[*head]->prev = newnode;

/* changing head */

[*head] = newnode;

}

/* Function to print nodes in a given linked list

This function is the same as printList[] of singly linked list */

void printList[Node* node]

{

while [node != NULL]

{

cout data next;

}

}

int main[]

{

/* Start with the empty list */

Node* head = NULL;

/* Let us create the linked list 2357 */

push[&head, 7];

push[&head, 5];

push[&head, 3];

push[&head, 2];

cout next]; /*delete middle node*/

deleteNode[&head, head->next]; /*delete last node*/

/* Modified linked list will be NULLNULL */

cout