Question

Done in C language using mobaxterm if you can but use basic C

This program is broken up into three different functions of insert, delete, and main. This program implements a queue of individual characters in a circular list using only a single pointer to the circular list; separate pointers to the front and rear elements of the queue are not used.

1. The linked list must be circular.  
     
2. The insert and remove operations must both be O(1)
     
3. You may use only one pointer into the queue from the outside; you may not have separate, named pointers for the front and the rear.

Test Cases:

1. Try to remove – thus making sure that the queue was initialized properly (i.e., empty)
2. Insert 'A', then do a remove, then another remove – thus making sure that you can empty the queue
3. Insert 'B', then 'F', do a remove, then insert 'D', then 'C', then do four removes (the last one should fail, of course). This test case will make sure your queue is FIFO – your last four removes should come out 'F', 'D', 'C', and then "cannot remove from an empty queue"

Answer 1

#include<stdio.h>
# define MAX 5
int cqueue_arr[MAX];
int front = -1;
int rear = -1;
void insert(int item)
{
if((front == 0 && rear == MAX-1) || (front == rear+1))
{
printf("Queue Overflow n");
return;
}
if(front == -1)
{
front = 0;
rear = 0;
}
else
{
if(rear == MAX-1)
rear = 0;
else
rear = rear+1;
}
cqueue_arr[rear] = item ;
}
void deletion()
{
if(front == -1)
{
printf("Queue Underflown");
return ;
}
printf("Element deleted from queue is : %dn",cqueue_arr[front]);
if(front == rear)
{
front = -1;
rear=-1;
}
else
{
if(front == MAX-1)
front = 0;
else
front = front+1;
}
}
void display()
{
int front_pos = front,rear_pos = rear;
if(front == -1)
{
printf("Queue is emptyn");
return;
}
printf("Queue elements :n");
if( front_pos <= rear_pos )
while(front_pos <= rear_pos)
{
printf("%d ",cqueue_arr[front_pos]);
front_pos++;
}
else
{
while(front_pos <= MAX-1)
{
printf("%d ",cqueue_arr[front_pos])
front_pos++;
}
front_pos = 0;
while(front_pos <= rear_pos)
{
printf("%d ",cqueue_arr[front_pos]);
front_pos++;
}
}
printf("n");
}
int main()
{
int choice,item;
do
{
printf("1.Insertn");
printf("2.Deleten");
printf("3.Displayn");
printf("4.Quitn");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1 :
printf("Input the element for insertion in queue : ");
scanf("%d", &item);
insert(item);
break;
case 2 :
deletion();
break;
case 3:
display();
break;
case 4:
break;
default:
printf("Wrong choicen");
}
}while(choice!=4);
return 0;
}

Another way :-

// C or C++ program for insertion and // deletion in Circular Queue #include<bits/stdc++.h> using namespace std; struct Queue {     // Initialize front and rear     int rear, front;     // Circular Queue     int size;     int *arr;     Queue(int s)     {        front = rear = -1;        size = s;        arr = new int[s];     }     void enQueue(int value);     int deQueue();     void displayQueue(); }; /* Function to create Circular queue */ void Queue::enQueue(int value) {     if ((front == 0 && rear == size-1) ||             (rear == (front-1)%(size-1)))     {         printf("\nQueue is Full");         return;     }     else if (front == -1) /* Insert First Element */     {         front = rear = 0;         arr[rear] = value;     }     else if (rear == size-1 && front != 0)     {         rear = 0;         arr[rear] = value;     }     else     {         rear++;         arr[rear] = value;     } } // Function to delete element from Circular Queue int Queue::deQueue() {     if (front == -1)     {         printf("\nQueue is Empty");         return INT_MIN;     }     int data = arr[front];     arr[front] = -1;     if (front == rear)     {         front = -1;         rear = -1;     }     else if (front == size-1)         front = 0;     else         front++;     return data; } // Function displaying the elements // of Circular Queue void Queue::displayQueue() {     if (front == -1)     {         printf("\nQueue is Empty");         return;     }     printf("\nElements in Circular Queue are: ");     if (rear >= front)     {         for (int i = front; i <= rear; i++)             printf("%d ",arr[i]);     }     else     {         for (int i = front; i < size; i++)             printf("%d ", arr[i]);         for (int i = 0; i <= rear; i++)             printf("%d ", arr[i]);     } } /* Driver of the program */ int main() {     Queue q(5);     // Inserting elements in Circular Queue     q.enQueue(A);   q.enQueue(B);     q.enQueue(F);     q.enQueue(D);     q.enQueue(C);     // Display elements present in Circular Queue     q.displayQueue();     // Deleting elements from Circular Queue     printf("\nDeleted value = %d", q.deQueue());     printf("\nDeleted value = %d", q.deQueue());     q.displayQueue();     q.enQueue(E);     q.enQueue(D);     q.enQueue(C);     q.displayQueue();     q.enQueue(20);     return 0; }