0018enqueue.cpp

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

typedef struct QNode
{
    int data;
    struct QNode * next;
    struct QNode * prev;
}QNode;

typedef struct MyQueue
{
    struct QNode * front;
    struct QNode * rear;
    int size;
}MyQueue;

QNode * getQNode(int data, QNode * prev)
{
    QNode * ref = (QNode * ) malloc(sizeof(QNode));
    if (ref == NULL)
    {
        return NULL;
    }
    ref->data = data;
    ref->next = NULL;
    ref->prev = prev;
    return ref;
}

MyQueue * getMyQueue()
{
    MyQueue * ref = (MyQueue * ) malloc(sizeof(MyQueue));
    if (ref == NULL)
    {
        return NULL;
    }
    ref->front = NULL;
    ref->rear = NULL;
    return ref;
}

void enqueue(MyQueue * ref, int data)
{
    QNode * node = getQNode(data, ref->rear);
    if (ref->front == NULL)
    {
        ref->front = node;
        ref->size = 1;
    }
    else
    {
        ref->rear->next = node;
        ref->size = ref->size + 1;
    }
    ref->rear = node;
}

int isEmpty(MyQueue * ref)
{
    if (ref->size == 0)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

int peek(MyQueue * ref)
{
    if (isEmpty(ref) == 1)
    {
        printf("\n Empty Queue");
        // When stack is empty
        return -1;
    }
    else
    {
        return ref->front->data;
    }
}

int isSize(MyQueue * ref)
{
    return ref->size;
}

int dequeue(MyQueue * ref)
{
    if (isEmpty(ref) == 1)
    {
        return -1;
    }
    else
    {
        int data = peek(ref);
        QNode * temp = ref->front;
        if (ref->front == ref->rear)
        {
            ref->rear = NULL;
            ref->front = NULL;
        }
        else
        {
            ref->front = ref->front->next;
            ref->front->prev = NULL;
        }
        ref->size--;
        return data;
    }
}
void printQdata(MyQueue * ref)
{
    QNode * node = ref->front;
    printf("\n Queue Element\n");
    while (node != NULL)
    {
        printf(" %d", node->data);
        node = node->next;
    }
    printf("\n");
}
int main()
{
    MyQueue * q = getMyQueue();
    enqueue(q, 1);
    enqueue(q, 3);
    enqueue(q, 5);
    enqueue(q, 6);
    enqueue(q, 7);
    printQdata(q);
    printf(" Size : %d", isSize(q));
    
    printf("\n Dequeue Node : %d", dequeue(q));
    printf("\n Dequeue Node : %d", dequeue(q));
    printf("\n Dequeue Node : %d", dequeue(q));
    printQdata(q);
    printf(" Size : %d\n", isSize(q));
      return 0;
}