1. /*
Linked List Implementation of Deque in C
Author: Kasun Ranga Wijeweera
Email: krw19870829@gmail.com
Date: 20130515
*/
#include<stdio.h>
#include<conio.h>
#include<alloc.h>
typedef struct dequeNode *link;
struct dequeNode
{
int data;
link next;
};
typedef struct
{
link front;
link rear;
}deque;

2. void initDeque(deque *d)
{
d->front=NULL;
d->rear=NULL;
}
int isEmpty(deque *d)
{
if((d->front)==NULL)
{
return 0;
}
else
{
return 1;
}
}
void putFront(deque *d,int x)
{
link t=(link)malloc(sizeof(struct dequeNode));
t->data=x;
t->next=NULL;

3. if(isEmpty(d))
{
t->next=d->front;
d->front=t;
}
else
{
d->front=t;
d->rear=t;
}
}
void putRear(deque *d,int x)
{
link t=(link)malloc(sizeof(struct dequeNode));
t->data=x;
t->next=NULL;
if(isEmpty(d))
{
d->rear->next=t;
d->rear=t;
}

4. else
{
d->front=t;
d->rear=t;
}
}
int getFront(deque *d)
{
link t=d->front;
int x=t->data;
if((d->front)==(d->rear))
{
d->front=NULL;
d->rear=NULL;
}
else
{
d->front=t->next;
}
free(t);
return x;
}

5. int getRear(deque *d)
{
link t=d->front;
link tr=d->rear;
int x=tr->data;
if(t==tr)
{
d->front=NULL;
d->rear=NULL;
}
else
{
while((t->next)!=tr)
{
t=t->next;
}
d->rear=t;
t->next=NULL;
}
free(tr);
return x;
}

6. void printDeque(deque *d)
{
link t=d->front;
while(t!=NULL)
{
printf("%d ",t->data);
t=t->next;
}
}
void main()
{
int x;
deque *d;
clrscr();
d=(deque*)malloc(sizeof(deque));
initDeque(d);
putFront(d,10);
putFront(d,20);
putRear(d,30);
putFront(d,40);

7. putRear(d,50);
putFront(d,60);
printf("n");
printDeque(d);
if(isEmpty(d))
x=getFront(d);
printf("n");
printDeque(d);
if(isEmpty(d))
x=getRear(d);
printf("n");
printDeque(d);
if(isEmpty(d))
x=getFront(d);
printf("n");
printDeque(d);
getch();

8. }