Build and use your own minimal queue class using an array of type String of fixe

Question

Build and use your own minimal queue class using an array of type String of fixed size to hold the queue.

The array should have the default size of 5.

The array size should be setable via a constructor.

The following methods must be implemented:

enqueue – inserts a value at the rear of the queue

dequeue – returns the value at the front of the queue, removing the value from the queue

isEmpty – returns true if the queue is empty, false otherwise

isFull - – returns true if the queue is full, false otherwise

Tip: In a queue of 2 or more elements, the index of the rear is “larger” than the index of the front – EXCEPT, the queue will need to “wrap around” the array. For example: If the array is 20 elements. the queue front is at index 15 and the queue rear is at index 19, the next enqueue will be at index 20, which doesn't exist. The index must “wrap around” the array, i. e. the next enqueue will be at index 0. The solution is to modulus by the array size whenever increasing an index, either rear of front. For example, to change the index of the rear to the next index,use the formula

rear = (rear + 1) % arraySize;

Explanation / Answer

#include <iostream>
using namespace std;
class CircularQueue
{
   private :
       string *arr ;//to array of string
       int F, R ;
       int MAX;
   public :
       CircularQueue( int size = 5 ) ;//constructor
       void enqueue ( string data ) ;//insert in queue
       string dequeue( ) ;//delete from queue
       bool isEmpty();//check if empty
       bool isFull();//check if full
       void display( ) ;
} ;

CircularQueue :: CircularQueue( int size )
{
   MAX = size ;
   arr = new string [ MAX ];//initialise array of string
   F = R = -1 ;
  
}
bool CircularQueue::isFull()
{

       if(( R + 1 ) % MAX == F)//its full
           return true;
       return false;
}
bool CircularQueue::isEmpty()
{
   if(F == -1 )//its empty
       return true;
   return false;
}
void CircularQueue :: enqueue ( string data )
{
   if ( isFull() )
   {
       cout << " Queue is full" ;
       return ;
   }
   R = ( R + 1 ) % MAX;//move to next
   arr[R] = data ;//inert data
   if ( F == -1 )
       F = 0 ;
}
string CircularQueue :: dequeue( )
{
   string data ;
   if ( isEmpty())//queue is empty
   {
       cout << " Queue is empty" ;
       return NULL ;
   }

   data = arr[F] ;
   arr[F] = "" ;
   if ( F == R )
   {
       F = -1 ;
       R = -1 ;
   }
   else
       F = ( F + 1 ) % MAX;
   return data ;
}
void CircularQueue :: display( )//display data in queue
{
   cout << endl ;
   for ( int i = 0 ; i < MAX ; i++ )
       cout << arr[i] << " " ;
   cout << endl ;
}
int main( )
{
   CircularQueue a (5) ;//create object of class
   a.enqueue ( "AKSHAY" ) ;
   a.enqueue ( "RAJ" ) ;
   a.enqueue ( "HEMANT" ) ;
   a.enqueue ( "JAYESH" ) ;
   a.enqueue ( "PRANAV" ) ;
  
   cout << " Elements in the circular queue: " ;
   a.display( ) ;
   string i = a.dequeue( ) ;
   cout << "data deleted: " << i ;
   i = a.dequeue( ) ;
   cout << " data deleted: " << i ;
   cout << " Elements in the circular queue after deletion: " ;
   a.display( ) ;
  
}

===========================================================

Output:

akshay@akshay-Inspiron-3537:~/Chegg$ g++ circularqueu.cpp
akshay@akshay-Inspiron-3537:~/Chegg$ ./a.out

Elements in the circular queue:
AKSHAY RAJ HEMANT JAYESH PRANAV
data deleted: AKSHAY
data deleted: RAJ
Elements in the circular queue after deletion:
HEMANT JAYESH PRANAV

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