Double Ended Queue or Deque

A Deque or deck is a Double Ended Queue. Allows elements to be added or removed on either the ends. Deque is a generalized version of a Queue data structure that allows insert and delete at both ends.

Operation in Double Ended Queue

• Insert an element at the back
• Insert an element at the front
• Remove element at front
• Remove element at the back

Graphical Representation.

Program for Deque.

view more:-Implementation of Quick Sort| Merge Sort| Heap Sort Algorithm.

Source code.

	/* dequeue*/
	#include<stdio.h>
	#include<stdlib.h>
	struct node
	{
		int data;
		struct node *addr;
	};
	struct node *rear,*head;

	void fdel();
	void rdel();
	void ins(int);
	void disp();
	
	int main()
	{
		ins(10);	
		ins(20);
		ins(30);
		ins(40);
		printf("Delete element from last\n");
		rdel(); //delete element from last
		rdel(); //delete elemeny from last
		printf("Delete element from last\n");
		fdel(); //delete element fron first
		fdel();//delete element fron first
		fdel();
	}
void ins (int val)
	{
		struct node *temp;
		temp=(struct node *)malloc(sizeof(struct node));
		temp->data=val;
		temp->addr=NULL;
		if (head==NULL)
		{
			head=temp;
			rear=temp;
		}
		else 
		{
			rear->addr=temp;
			rear=temp;
		}
		disp();
	}
void disp()
	{
		struct node *i=head;
		printf("queue: ");
		while(i!=NULL)
		{
		printf("%d ",i->data);
		i=i->addr;
		}	
		printf("\n  ");
	}
	
	void fdel()
	 {
	//if queue is empty
	if(head==NULL)
		printf("Error:empty\n");
	//else
	else
	{	
	//more than one node exist
	head=head->addr;
	//only one node exist
	if(head==NULL)
		rear=NULL;
	}
	//display
	disp();
	}
	void rdel()
	{
		struct node *i=head;
		if(head!=NULL)
		{
			while(i->addr!=rear)
			{
				i=i->addr;
			}
			i->addr=NULL;
			rear=i;
			if(rear==NULL)
			{
				head=NULL;
			}
			disp();
		}
	}	/* dequeue*/

Output.

queue: 10
queue: 10 20
queue:10 20 30
queue: 10 20 30 40
Delete element from last
queue: 10 20 30
queue: 10 20
Delete element from last
queue: 20
queue:
Error:empty
queue:

Source:-greekforgreek