Styjun

The code is supposed to do queue functions which I got right.

The only problem I am having is: I am supposed to double the array size to twice its original size once the array gets completely filled.

I have coded for it but still getting garbage values when I try to put in more values than the original array size. So the problem seems to be in the inc() function below:

#ifndef Q_H_
#define Q_H_

#include <iostream>
using namespace std;



template <class elemType>
class arrayQueue

 int size;
 int *array;
 int front;
 int back;
 int count;

public:
 arrayQueue(elemType size)

 this->size = size;
 array = new int[size];
 front = 0;
 back = -1;
 count=0;


 bool isEmpty()
 
 return (max()==0);
 

 bool isFull() 
 return (max()==size);
 

 void enqueue(elemType entry)
 
 cout << "enqueue " << entry;

 if(isEmpty())
 
 front = back = 0;
 array[back] = entry;
 count++;
 
 else
 
 back = (back+1) % size;
 array[back] = entry;
 count++;
 
 cout << endl;
 

 int maxsize()
 
 return count;
 

 void dequeue() 
 cout << "dequeue : " << Front();
 if(isEmpty())
 
 cout << " error : empty";
 
 else if(back == front)
 
 back = front = -1;
 
 else
 
 front = (front+1) % size;
 count--;
 
 cout << endl;
 

 void print()
 
 if(isEmpty())
 
 cout << "Queue is empty";
 
 else
 
 for(int i = front; i<count; i++)
 
 cout << array[i] << " ";
 
 cout << array[back];

 
 //cout<<"count is:" <<count<<endl;
 cout << endl;
 

 int Front()
 

 if(front == -1)
 
 cout<<"Queue is emptyn";
 return -1;
 
 return array[front];

 

 int Back()
 
 if(back==-1)
 
 cout<<"Queue is full";
 
 return array[back];
 

 int max()
 
 return count;
 cout <<"count: " <<count;

 

 void inc()
 
 int newsize = this->size*2;

 elemType *temp = new elemType[newsize];



 for (int i=0; i<this->count;i++)
 
 temp[i]=this->array[(front+i) % size];
 

 delete [] this->array;
 this->array=temp;
 this->count=newsize;

// front=array[front]; //0
 //front = 0;
 //back=count;


 


;



#endif /* Q_H_ */

I would really appreciate help with this.

three small changes:

1. 
   

   enqueue method: inc when isFull

   
   
   

   if (isFull())
   
    inc();
   
   

   
   



2. print method: print every element from front to back



3. 
   

   inc method: copy every element from front to back, and reset front and back index

   
   
   

   void inc()
   
    int newsize = this->size*2;
   
    elemType *temp = new elemType[newsize];
   
    // ******* IMPORTANT ******
    // copy count elements
    for (int i = 0; i < count; ++i) 
    int index = (front + i) % size;
    temp[i] = array[index];
    
    front = 0;
    back = count - 1;
    delete []array;
    array=temp;
    count=newsize;
   
   

   
   

 template <class elemType>
 class arrayQueue
 
 int size;
 int *array;
 int front;
 int back;
 int count;
 public:
 arrayQueue(elemType size)
 
 this->size = size;
 array = new int[size];
 front = 0;
 back = -1;
 count=0;
 

 bool isEmpty()
 
 return (max()==0);
 

 bool isFull() 
 return (max()==size);
 

 void enqueue(elemType entry)
 
 cout << "enqueue " << entry;

 if(isEmpty())
 
 front = back = 0;
 array[back] = entry;
 count++;
 
 else
 
 if (isFull()) 
 inc();
 
 back = (back+1) % size;
 array[back] = entry;
 count++;
 
 cout << endl;
 

 int maxsize()
 
 return count;
 

 void dequeue() 
 cout << "dequeue : " << Front();
 if(isEmpty())
 
 cout << " error : empty";
 
 else if(back == front)
 
 back = front = -1;
 
 else
 
 front = (front+1) % size;
 count--;
 
 cout << endl;
 

 void print()
 
 if(isEmpty())
 
 cout << "Queue is empty";
 
 else
 
 // ******* IMPORTANT ******
 for (int i = 0; i < count; ++i) 
 int index = (front + i) % size;
 cout << array[index] << " ";
 
 
 //cout<<"count is:" <<count<<endl;
 cout << endl;
 

 int Front()
 

 if(front == -1)
 
 cout<<"Queue is emptyn";
 return -1;
 
 return array[front];

 

 int Back()
 
 if(back==-1)
 
 cout<<"Queue is full";
 
 return array[back];
 

 int max()
 
 return count;
 cout <<"count: " <<count;

 

 void inc()
 
 int newsize = this->size*2;

 elemType *temp = new elemType[newsize];

 // ******* IMPORTANT ******
 // copy count elements
 for (int i = 0; i < count; ++i) 
 int index = (front + i) % size;
 temp[i] = array[index];
 

 front = 0;
 back = count - 1;
 delete []array;
 array = temp;
 count = newsize;
 
 ;

Since you move elements to the beginning of the newly allocated array, inc needs to update front and back to refer to their respective new positions.

Also, you're updating count to be the new size instead of size.