Question

You are working for one of the big airlines. Your manager asks you to create a sample program using queue data structure that explains how to board in the aircraft. Be sure to implement following things: Implement Queue data structure Enqueue Bonnai, Tim, Jerry and tom Display the front of the queue. It should be Bonnai Display the end of the queue. It should be Tom You need to perform following tasks to implement above example as queue data structure. Define the queue Add customernames one by one into the queue Print the front element Print the back element

Answer 1

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

// A linked list (LL) node to store a queue entry
struct QNode
{
   char *key;
   struct QNode *next;
};

// The queue, front stores the front node of LL and rear stores the
// last node of LL
struct Queue
{
   struct QNode *front, *rear;
};

// A utility function to create a new linked list node.
struct QNode* newNode(char k[])
{
   struct QNode *temp = (struct QNode*)malloc(sizeof(struct QNode));
   temp->key = k;
   temp->next = NULL;
   return temp;
}

// A utility function to create an empty queue
struct Queue *createQueue()
{
   struct Queue *q = (struct Queue*)malloc(sizeof(struct Queue));
   q->front = q->rear = NULL;
   return q;
}

// The function to add a key k to q
void enQueue(struct Queue *q, char k[])
{
   // Create a new LL node
   struct QNode *temp = newNode(k);

   // If queue is empty, then new node is front and rear both
   if (q->rear == NULL)
   {
   q->front = q->rear = temp;
   return;
   }

   // Add the new node at the end of queue and change rear
   q->rear->next = temp;
   q->rear = temp;
}
/*
// Function to remove a key from given queue q
struct QNode *deQueue(struct Queue *q)
{
   // If queue is empty, return NULL.
   if (q->front == NULL)
   return NULL;

   // Store previous front and move front one node ahead
   struct QNode *temp = q->front;
   q->front = q->front->next;

   // If front becomes NULL, then change rear also as NULL
   if (q->front == NULL)
   q->rear = NULL;
   return temp;
}*/

int main()
{
   struct Queue *q = createQueue();   //create queue data structure using createQueue() function
   enQueue(q,"Bonnai"); //enqueue Bonnai
   enQueue(q,"Tim");       //enqueue Tim
   enQueue(q,"Jerry");     //enqueue Jerry
   enQueue(q,"Tom");      //enqueue Tom
   printf("Queue front : ");
   printf("%s\n",q->front->key); //q->front points to the front node and key points to the data element of front node
   printf("Queue rear : ");
   printf("%s\n",q->rear->key);    //q->rear points to the rear node and key points to the data element of rear node
   return 0;
}