This C++ program displays the nodes of a doubly linked list in which linked list can be traversed from the last node to first node or vice versa.

Here is the source code of the C++ program to display the values present in the nodes from head to the tail and in reverse. This C++ program is successfully compiled and run on DevCpp, a C++ compiler. The program output is given below.

`/*`

`* C++ Program to Implement Sorted Doubly Linked List`

`*/`

`#include<stdio.h>`

`#include<conio.h>`

`#include<iostream>`

using namespace std;

int c = 0;

`struct node`

`{`

node *next, *prev;

int data;

}*head = NULL, *tail = NULL, *p = NULL, *r = NULL, *np = NULL;

void create(int x)

`{`

np = new node;

np->data = x;

np->next = NULL;

np->prev = NULL;

if (c == 0)

`{`

tail = np;

head = np;

p = head;

p->next = NULL;

p->prev = NULL;

c++;

`}`

`else`

`{`

p = head;

r = p;

if (np->data < p->data)

`{`

np->next = p;

p->prev = np;

np->prev = NULL;

head = np;

p = head;

`do`

`{`

p = p->next;

`}`

while (p->next != NULL);

tail = p;

`}`

else if (np->data > p->data)

`{`

while (p != NULL && np->data > p->data)

`{`

r = p;

p = p->next;

if (p == NULL)

`{`

r->next = np;

np->prev = r;

np->next = NULL;

tail = np;

break;

`}`

else if (np->data < p->data)

`{`

r->next = np;

np->prev = r;

np->next = p;

p->prev = np;

if (p->next != NULL)

`{`

`do`

`{`

p = p->next;

`}`

while (p->next !=NULL);

`}`

tail = p;

break;

`}`

`}`

`}`

`}`

`}`

void traverse_tail()

`{`

node *t = tail;

while (t != NULL)

`{`

cout<<t->data<<"\t";

t = t->prev;

`}`

cout<<endl;

`}`

void traverse_head()

`{`

node *t = head;

while (t != NULL)

`{`

cout<<t->data<<"\t";

t = t->next;

`}`

cout<<endl;

`}`

int main()

`{`

int i = 0, n, x, ch;

cout<<"enter the no of nodes\n";

cin>>n;

while (i < n)

`{`

cout<<"\nenter value of node\n";

cin>>x;

create(x);

i++;

`}`

cout<<"\nTraversing Doubly Linked List head first\n";

traverse_head();

cout<<"\nTraversing Doubly Linked List tail first\n";

traverse_tail();

getch();

`}`

Output enter the no of nodes 7 enter value of node 4 enter value of node 2 enter value of node 8 enter value of node 1 enter value of node 9 enter value of node 6 enter value of node 3 Traversing Doubly Linked List head first 1 2 3 4 6 8 9 Traversing Doubly Linked List tail first 9 8 6 4 3 2 1

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