/* Program to implement deque using arrays*/
//include header files
#include<stdio.h>
#include<conio.h>

int deque[5];
long front,rear;

 

//Function to initialise the deque
void initdeque();

//Function to add an element in the beginning
void enqueBeg(int);

//Function to add an element in the end
void enqueEnd(int );

//Function to serve an element from the beginning
void dequeueBeg();

//Function to serve an element from the end
void dequeueEnd();

//Function to display the deque elements
void display ( );

 

void main()
{
int info,choice;

//To initialise..
initdeque(); //Function call

while(1)//at least it will run for once
{
//Displaying menu
clrscr();
printf(" MENU\n");
printf("1. En-queue/Append in the beginning\n");
printf("2. En-queue/Append in the end\n");
printf("3. De-queue/Serve from the beginning\n");
printf("4. De-queue/Serve from the end\n");
printf("5. Display\n");
printf("6. Exit\n");

printf("Your choice: ");
scanf("%i",&choice);

switch(choice)
{
case 1: printf("Enter the element to be added in the beginning:");
scanf("%i",&info);

enqueBeg(info); //Function call for adding at the beginning.

getch();
break;

case 2: printf("Enter the element to be added in the end: ");
scanf("%i",&info);

enqueEnd(info); //Function call[En-queue/Append in the end]

getch();
break;

case 3: dequeueBeg(); //Function call for deleitng from begining.[De-queue/Serve from the beginning]

getch();
break;

case 4: dequeueEnd(); //Function call for deleitng at the end.[De-queue/Serve from the end]
getch();
break;

case 5: display(); //Function call
getch();
break;

case 6: exit();
break;

default: printf("You entered wrong choice!");
getch();
}
}
}

void initdeque()//initialising the deque.
{
front=rear=-1;
}

void enqueBeg()
{
int i,info;

//If dequeue is empty then first element can be simply added
if(front==-1)
{
front=rear=0;//both fornt,rear point to first element.

deque[front]=info;

}

//If the deque is full from the front only...
if(front==0 && rear!=5-1)
{
//...shift the elements from 1 posn to it's right
for(i=rear;i>=front;i--)
deque[i+1]=deque[i];

//Index no. of last element should be incremented after shifting
rear++;

//New element will be added in the front of deque
deque[front]=info;

}

//if the deque is empty from the front...
else if(front>0)
{
front--;

//...new element will be accomodated in the empty cell
deque[front]=info;
}

}

void enqueEnd()
{
int i,info;

//If dequeue is empty then first element can be simply added
if(front==-1)
{
front=rear=0;
deque[front]=info;

}

//If the deque is full from the end only...
if(front!=0 && rear==5-1)
{
//...shift the elements from 1 posn to its left
for(i=front;i<=rear;i++)
deque[i-1]=deque[i];

//Index no. of first element should be decremented after shifting
front++;

//New element will be added in the end of deque
deque[rear]=info;
}

//if the deque is empty from the end...
else if(rear<5-1)
{
rear++;
//...new element will be accomodated in the empty cell
deque[rear]=info;
}
return 1;
}

void dequeueBeg()
{
int info;

//If the deque is empty...
if(front==-1)
{
return 0; //End of function
}

//Else
//Extracting info & setting flag
info=deque[front];
deque[front]=0;

//Setting front
if(front==rear)
front=rear=-1; //As the deque will become empty

else
front++; //Front cell is unoccupied now

return info; //Returning the info
}

void dequeueEnd()
{
int info;

//If the deque is empty...
if(front==-1)
{
return 0; //End of function
}

//Else
//Extracting info & setting flag
info=deque[rear];

deque[rear]=0;

//Setting rear
if(front==rear)
front=rear=-1; //As the deque will become empty
else
rear--; //Rear cell is unoccupied now

return info; //Returning the info
}

/*displays the curent position of the dqueue*/
void display ()
{
int i;

//Displaying the deque elments
for(i=front;i<=rear;i++)
printf("%i\n",deque[i]);
}

/*output of the program*/
MENU
1. En-queue/Append in the beginning
2. En-queue/Append in the end
3. De-queue/Serve from the beginning
4. De-queue/Serve from the end
5. Display
Your choice
1

enter the element to be added at the beginning
5
MENU
1. En-queue/Append in the beginning
2. En-queue/Append in the end
3. De-queue/Serve from the beginning
4. De-queue/Serve from the end
5. Display
6. Exit
Your choice:
2

enter the element to be added at the end
50

 

MENU
1. En-queue/Append in the beginning
2. En-queue/Append in the end
3. De-queue/Serve from the beginning
4. De-queue/Serve from the end
5. Display
6. Exit
Your choice:
3

enter the element to be deleted from the beginning
5

MENU
1. En-queue/Append in the beginning
2. En-queue/Append in the end
3. De-queue/Serve from the beginning
4. De-queue/Serve from the end
5. Display
6. Exit
Your choice:
4

enter the element to be deleted from the end
50

MENU
1. En-queue/Append in the beginning
2. En-queue/Append in the end
3. De-queue/Serve from the beginning
4. De-queue/Serve from the end
5. Display
6. Exit
Your choice:
6