////////////////////////////////////////////////////////////////////////////////

//INCLUDES

#include <stdio.h>

#include <stdlib.h>

////////////////////////////////////////////////////////////////////////////////

//MACROS: CONSTANTS

////////////////////////////////////////////////////////////////////////////////

//DATA STRUCTURES

struct node {

int data;

struct node* next;

struct node* pre;

} *head, *tail, *tmp;

////////////////////////////////////////////////////////////////////////////////

//GLOBAL VARIABLES

int count;

////////////////////////////////////////////////////////////////////////////////

//FORWARD DECLARATIONS

void create();

void enque(int x);

int deque();

int peek();

int size();

int isEmpty();

////////////////////////////////////////////////////////////////////////////////

//MAIN ENTRY POINT

int main(int argc, char const *argv[]) {

create();

enque(5);

return 0;

}

void create() {

head = NULL;

tail = NULL;

}

/**

* Puts an item into the Queue.

*/

void enque(int x) {

if(head == NULL) {

head = (struct node *)malloc(1 * sizeof(struct node));

head->data = x;

head->pre = NULL;

tail = head;

} else {

tmp = (struct node *)malloc(1 * sizeof(struct node));

tmp->data = x;

tmp->next = tail;

tail = tmp;

}

}

/**

* Takes the next item from the Queue.

*/

int deque() {

int returnData = 0;

if(head == NULL) {

printf("ERROR: Deque from empty queue.\n");

exit(1);

} else {

returnData = head->data;

if(head->pre == NULL)

head = NULL;

else

head = head->pre;

head->next = NULL;

}

return returnData;

}

/**

* Returns the size of the Queue.

*/

int size() {

return count;

}