Dequeue

#include <iostream>
using namespace std;
void push_l (int n);	//prototype
void push_r (int n);	//prototype
int pop_l (int &n);		//prototype
int pop_r (int &n);		//prototype

struct elem
{
	int key;
	elem *next;
}
*leftt = NULL, *rightt = NULL;

void push_l (int n)
{
	elem *p;
	p = leftt;
	leftt = new elem;
	leftt->key = n;
	leftt->next = p;
	if (rightt == NULL)
	{ //добавяне в празен дек
	   rightt = leftt;
	}
}

void push_r (int n)
{
	elem *p;
	p = rightt;
	rightt = new elem;
	rightt->key = n;
	rightt->next = NULL;
	if (leftt == NULL)	//добавяне на първи елемент
  		leftt = rightt;
	else
  		p->next = rightt;
}

int pop_l (int &n)
{
	elem *p;
	if (leftt)
	{
		n = leftt->key;
   		p = leftt;
  		leftt = leftt->next;
  		if (leftt == NULL) //последен елемент
     		rightt = NULL;
		delete p;
		return 1;
	} //if(leftt)
	else
   		return 0;
}

int pop_r (int &n)
{
	elem *p;
	if (rightt)
	{
   		n = rightt->key;
   		if (leftt == rightt) //последен елемент
     	{
		 	delete rightt;
      		leftt = rightt = NULL;
      	}
   		else //leftt==rightt
     	{
		 	p = leftt;
      		while (p->next != rightt)
         		p = p->next;
      		p->next = NULL;
     		delete rightt;
     		rightt = p;
      	}
		return 1;
	} //rigth
	else
   		return 0;
}

int main()
{
	int ch;
	do
	{
		int num;
		cout<<"\n		Menu:\n";
		cout<<"1 - Input leftt\n";
		cout<<"2 - Input rightt\n";
		cout<<"3 - Output leftt\n";
		cout<<"4 - Output rightt\n";
		cout<<"5 - Exit\n";
		cout<<"Your choice: ";
		cin>>ch;
		switch (ch)
		{
			case (1):
			case (2):
			cout<<"\nInput number: ";
			cin>>num;
			if (ch==1)
				push_l(num);
			else
				push_r(num);
			break;
			case (3):
			{
				if (leftt==NULL)
				cout <<" The Deque is empty!";
				while (pop_l(num))
					cout<<num<<"\t";
				break;
			} //case(3)
			case (4):
			{
				if (rightt == NULL)
					cout <<" The Deque is empty!";
				while(pop_r(num))
					cout<<num<<"\t";
			} //case(4)
		} //switch
	} while (ch!=5);
	return 0;
} //main()