12_DeQueue.cpp

/*
A double-ended queue (deque) is a linear list in which additions and deletions may be made at either end. Obtain a data
representation mapping a deque into a one-dimensional array. Write C++ program to simulate deque with functions to add 
and delete elements from either end of the deque. 
*/

#include<iostream>
#include<stdio.h>
#define MAX 10
using namespace std;

struct que
{
    int arr[MAX];
    int front,rear;
};

void init(struct que *q)
{
    q->front=-1;
    q->rear=-1;
}

void print(struct que q)
{
    int i;
    i=q.front;
    while(i!=q.rear)
    {
        cout<<"\t"<<q.arr[i];
        i=(i+1)%MAX;
    }
    cout<<"\t"<<q.arr[q.rear];
}

int isempty(struct que q)
{
    return q.rear==-1?1:0;
}

int isfull(struct que q)
{
    return (q.rear+1)%MAX==q.front?1:0;
}

void addf(struct que *q,int data)
{
    if(isempty(*q))
    {
        q->front=q->rear=0;
        q->arr[q->front]=data;
    }
    else
    {
        q->front=(q->front-1+MAX)%MAX;
        q->arr[q->front]=data;
    }
}

void addr(struct que *q,int data)
{
    if(isempty(*q))
    {
        q->front=q->rear=0;
        q->arr[q->rear]=data;
    }
    else
    {
        q->rear=(q->rear+1)%MAX;
        q->arr[q->rear]=data;
    }
}

int delf(struct que *q)
{
    int data1;
    data1=q->arr[q->front];
    if(q->front==q->rear)
        init(q);
    else
        q->front=(q->front+1)%MAX;
    return data1;
}

int delr(struct que *q)
{
    int data1;
    data1=q->arr[q->rear];
    if(q->front==q->rear)
        init(q);
    else
        q->rear=(q->rear-1+MAX)%MAX;
    return data1;
}

int main()
{
    struct que q;
    int data,ch;
    init(&q);
    while(ch!=6)
    {
        cout<<"\t\n1.Insert front"
                "\t\n2.Insert rear"
                "\t\n3.Delete front"
                "\t\n4.Delete rear"
                "\t\n5.Print"
                "\t\n6.Exit";
         cout<<"\nEnter your choice : ";
        cin>>ch;
        switch(ch)
        {
           case 1:
              cout<<"\nEnter data to insert front : ";
              cin>>data;
              addf(&q,data);
              break;

           case 2:
               cout<<"\nEnter the data to insert rear : ";
               cin>>data;
               addr(&q,data);
               break;

           case 3:
               if(isempty(q))
                   cout<<"\nDequeue is empty!!!";
               else
               {
                   data=delf(&q);
                   cout<<"\nDeleted data is : "<<data;
               }
               break;

           case 4:
               if(isempty(q))
                   cout<<"\nDequeue is empty!!!";
               else
               {
                   data=delr(&q);
                   cout<<"\nDeleted data is : "<<data;
               }
               break;

           case 5:
                if(isempty(q))
                    cout<<"\nDequeue is empty!!!";
                else
                {
                    cout<<"\nDequeue elements are : ";
                    print(q);
                }
                break;
        }
    }
    return 0;
}