#include

class Node $\{$

public:

int value;

Node$*$ next;

Node$($int value $=0)\{$

this$->$value $=$ value;

this$->$next $=$ nullptr;

$\}$

$\}$;

class Queue $\{$

private:

Node$*$ front$\_$node;

Node$*$ rear$\_$node;

public:

Queue$()\{$

this$->$front$\_$node $=$ nullptr;

this$->$rear$\_$node $=$ nullptr;

$\}$

bool isEmpty$()\{$

return this$->$front$\_$node $==$ nullptr;

$\}$

void enqueue$($int value$)\{$

Node$*$ new$\_$node $=$ new Node$($value$)$;

if $($this$->$rear$\_$node $==$ nullptr$)\{$

$//$ If the queue is empty, both front and rear nodes will point to the new node

this$->$front$\_$node $=$ this$->$rear$\_$node $=$ new$\_$node;

$\}$ else $\{$

$//$ Attach the new node to the end of the queue and update the rear node

this$->$rear$\_$node$->$next $=$ new$\_$node;

this$->$rear$\_$node $=$ new$\_$node;

$\}$

$\}$

int dequeue$()\{$

if $($this$->$isEmpty$())\{$

throw std::out$\_$of$\_$range$("$dequeue from empty queue"$)$;

$\}$

int value $=$ this$->$front$\_$node$->$value;

this$->$front$\_$node $=$ this$->$front$\_$node$->$next;

if $($this$->$front$\_$node $==$ nullptr$)\{$

$//$ If the queue becomes empty after dequeue, reset the rear$\_$node as well

this$->$rear$\_$node $=$ nullptr;

$\}$

return value;

$\}$

int front$()\{$

if $($this$->$isEmpty$())\{$

throw std::out$\_$of$\_$range$("$front from empty queue"$)$;

$\}$

return this$->$front$\_$node$->$value;

$\}$

$\}$;

int main$()\{$

Queue queue;

std::cout $<<$ std::boolalpha $<<$ queue.isEmpty$()<<$ std::endl; $//$ Output: true

queue.enqueue$(1)$;

queue.enqueue$(2)$;

queue.enqueue$(3)$;

std::cout $<<$ std::boolalpha $<<$ queue.isEmpty$()<<$ std::endl; $//$ Output: false

std::cout $<<$ queue.front$()<<$ std::endl; $//$ Output: $1$

std::cout $<<$ queue.dequeue$()<<$ std::endl; $//$ Output: $1$

std::cout $<<$ queue.front$()<<$ std::endl; $//$ Output: $2$

std::cout $<<$ queue.dequeue$()<<$ std::endl; $//$ Output: $2$

std::cout $<<$ queue.front$()<<$ std::endl; $//$ Output: $3$

std::cout $<<$ queue.dequeue$()<<$ std::endl; $//$ Output: $3$

std::cout $<<$ std::boolalpha $<<$ queue.isEmpty$()<<$ std::endl; $//$ Output: true

return $0$;

$\}$