How can I make it so in this program we have to make the linked list first before any of the other options can be chosen.

#include

using namespace std;

struct node$\{$

int data;

struct node$*$ prev;

struct node$*$ next;

$\}$;

$//$To insert a new number in the doubly linked list

void Add$($node$**$ head,int x$)\{$

struct node$*$ temp$=*$head;

while$($temp$!=$NULL$)\{$

if$($temp$->$data$==$x$)\{$

cout$<<$"Number already exists.";

return;

$\}$

temp$=$temp$->$next;

$\}$

$//$create a new node

node$*$ newnode $=$ new node;

newnode$->$data$=$x;

newnode$->$next$=$NULL;

newnode$->$prev$=$NULL;

$//$if the linked list is empty

if$(*$head$==$NULL$)\{$

$*$head$=$newnode;

return;

$\}$

$//$else

else$\{$

$//$To insert in the beginning

if$((*$head$)->$data$>$newnode$->$data$)\{$

newnode$->$next$=*$head;

newnode$->$next$->$prev$=$newnode;

$*$head$=$newnode;

$\}$

$//$To insert in between and in end

else$\{$

struct node$*$ curr$=*$head;

while$($curr$->$next!$=$NULL && curr$->$next$->$datadata$)\{$

curr$=$curr$->$next;

$\}$

newnode$->$next$=$curr$->$next;

if$($curr$->$next!$=$NULL$)$

newnode$->$next$->$prev$=$newnode;

curr$->$next$=$newnode;

newnode$->$prev$=$curr;

$\}$

$\}$

$\}$

$//$To delete a number from doubly linked list

int Delete$($struct node$**$ head,int x$)\{$

if$(*$head $==$ NULL$)\{$

cout$<<$"The linked list is empty.";

return $-1$;

$\}$

$//$To delete from beginning

if$((*$head$)->$data$==$x$)\{$

$*$head$=(*$head$)->$next;

return $1$;

$\}$

$//$To delete in between or from end

struct node$*$ curr$=*$head;

while$($curr$->$data!$=$x && curr$->$next!$=$NULL$)\{$

curr$=$curr$->$next;

$\}$

if$($curr$->$data!$=$x$)\{$

return $0$;

$\}$

if$($curr$->$next!$=$NULL$)\{$

curr$->$next$->$prev$=$curr$->$prev;

$\}$

if$($curr$->$prev!$=$NULL$)\{$

curr$->$prev$->$next$=$curr$->$next;

$\}$

return $1$;

$\}$

$//$To display the doubly linked list

void displayDLL$($struct node$*$ head$)\{$

while$($head$!=$NULL$)\{$

cout$<<$"Number: $"<$data$<<"$

$"$;

head$=$head$->$next;

$\}$

$\}$

$//$To search in the doubly linked list

int Search$($struct node$*$ head, int x$)\{$

int count$=0$;

while$($head$!=$NULL$)\{$

$//$To count the position of the number

count$++$;

if$($head$->$data$==$x$)\{$

return count;

$\}$

head$=$head$->$next;

$\}$

$//$if reaches here, that means number was not found

return $-1$;

$\}$

$//$To modify the doubly linked list

void Modify$($struct node$**$ head,int s$,$int f$)\{$

$//$check if the head node is the one we are searching for

struct node$*$ curr$=*$head;

if$($Search$($curr$,$s$)==-1)\{$

cout$<<$"The number you want to modify doesn't exist.";

return;

$\}$

while$($curr$!=$NULL$)\{$

if$($curr$->$data$==$f$)\{$

cout$<<$"The number you want to change to already exists.";

return;

$\}$

curr$=$curr$->$next;

$\}$

Delete$($head$,$s$)$;

Add$($head$,$f$)$;

cout$<<$"The number is modified.";

$\}$

$//$To delete the entire doubly linked list

void deleteEntireList$($struct node$**$ head$)\{$

struct node$*$ temp;

while$(*$head$!=$NULL$)\{$

temp$=*$head;

$*$head$=(*$head$)->$next;

free$($temp$)$; $//$to free the memory of the node

$\}$

$\}$

int main$()\{$

struct node$*$ head;

int choice;

cout$<<$"Pick a task from the menu below:

$"$;

cout$<<"********************************$

$"$;

cout$<<"1.$ Create

$2.$ Add

$3.$ Delete

$4.$ Display";

cout$<<"$

$5.$ Modify

$6.$ Purge entire list

$7.$ Search for node

$8.$ Exit the program";

cout$<<"$

$********************************$

$"$;

do$\{$

cout$<<$"User's task pick: $"$;

cin$>>$choice;

cout$<<"--------------------------------$

$"$;

if$($choice$==1)\{$

head$=$NULL;

cout$<<$"Linked List created.";

$\}$

else if$($choice$==2)\{$

int x;

cout$<<$"Enter a value to add: $"$;

cin$>>$x;

Add$($&head,x$)$;

cout$<<$"Number added to list.";

$\}$

else if$($choice$==3)\{$

int x;

cout$<<$"What would you like to delete: $"$;

cin$>>$x;

x$=$Delete$($&head,x$)$;

if$($x$==1)\{$

cout$<<$"Number is deleted from linked list.";

$\}$

else$\{$

cout$<<$"Number not found.";

$\}$

$\}$

else if$($choice$==4)\{$

if$($head$==$NULL$)\{$

cout$<<$"End of linked list.";