dequeue.cpp

#include<stdio.h>
#include<stdlib.h>


#define NULL_VALUE -99999
#define SUCCESS_VALUE 99999

struct listNode
{
    int item;
    struct listNode * next;
};




class dequeue
{
    struct listNode * list;
    struct listNode * tail;
public:
    dequeue()
    {
        list=0;
        tail=0;

    }
    int Push_front(int Item)
    {

        struct listNode * newNode ;
        newNode = (struct listNode*) malloc (sizeof(struct listNode)) ;
        newNode->item = Item ;
        if(list==0)
        {
            list=newNode;
            list->next=0;
            tail=newNode;
            tail->next=0;
            return SUCCESS_VALUE;
        }
        if(list->next==0)
        {
            tail=list;
            newNode->next=list;
            list=newNode;
            return SUCCESS_VALUE;
        }
        newNode->next=list;
        list=newNode;
        return SUCCESS_VALUE;
    }
    int Push_back(int item)
    {

        struct listNode * newNode ;
        newNode = (struct listNode*) malloc (sizeof(struct listNode)) ;
        newNode->item = item ;
        if(tail==0)
        {
            tail=newNode;
            tail->next=0;
            return SUCCESS_VALUE;
        }

        tail->next=newNode;
        newNode->next=0;
        tail=newNode;
        return SUCCESS_VALUE;
    }
    int Pop_front()
    {

        if(list==0)
        {
            return NULL_VALUE;

        }
        listNode *temp=list;

        list=list->next;
        free(temp);

        return SUCCESS_VALUE;
    }
    int Pop_back()
    {
        if(tail==0)
        {
            return NULL_VALUE;

        }
        listNode *temp=list;
        while(temp->next!=tail)
        {
            temp=temp->next;
        }
        tail=temp;
        tail->next=0;

        return SUCCESS_VALUE;
    }
    void Print()
    {
        struct listNode * temp;
        temp = list;
        while(temp!=0)
        {
            printf("%d->", temp->item);
            temp = temp->next;
        }
        printf("\n");
    }
};


int main(void)
{
    dequeue s;
    s.Push_front(4);
    s.Print();
    s.Push_back(-1);
    s.Print();
    s.Pop_back();
    s.Print();


}