max/min of an array of OBJECTS

MaxGreen (115)
I am writing a code using class ( objects ) which will display a menu consisting of 6 options like :

1. create an array of "n" elements objects
2. display of the array
3. save information in a FILE ( using OOP)
4. load information
5. find the maximum element & find the minimum element
6. find the sum of the elements


I find it difficult to adjust the method finding the max and min for objects
, your reference and advice will be high appreciated, 

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class array
{
	public:
		void setN(){cout<<"Enter N ::: "; cin>>this->N;}
		
		void setV(){cout<<"Enter value ::: "; cin>>value;}
		void setVA(int value){ this->value=value;}
		
		const int getV()const{return this->value;}
		const int getN()const{return this->N;}
		
		array(int value=NULL){this->value=value; this->N=NULL;}
		array(int value, int N){this->value=value;}
		
		array(const array&Obj){this->value=Obj.value; this->N=Obj.N;}
		
	~array(){}
	
		friend ostream &operator<<(ostream&out, array&Obj);
		
	    friend void create(array&);
	    
	    friend void display(array&);
	    
	    friend void save(array&);
	    
	    friend int menu(array&);
	    
	    friend int max(array&);
	    
	    friend int min(array&);
	    
	    friend int sum(array&);
	   
	    
	protected:
		
	int value;
	int N;
};

		 ostream &operator<<(ostream&out, array&Obj)
		{
			out<<"Array ="<<Obj.value;
			return out;
		}
		

 
		void create(array&X)
		{

         for(int i=0; i<X.getN(); i++)
          {
 	       X.setV();
          }
		}
		
		
		void display(array&X)
		{

         for(int i=0; i<X.getN(); i++)
         {
 	       cout<<"\n A "<<"["<<i<<"]"<<X.getV();
         }
		}
        
        int max( array&X )
        {
        	
        int max=INT_MIN;
        	
        	  for(int i=1; i<X.getN(); i++)
         {
 	        if( max < (X.getV) max=(X.getV);
         }
         return max;
		}
        /*
        void save(array&X)
        {
          string FN;
  
  cout<<" Enter File name = "; cin >> FN;

  FN+=".txt";
  
  fstream F;
  
   F.open(FN.c_str(),  ios::out );
   
   if( F.fail() ) cerr<<" Error Fstream FILE "<<endl; 
   else cout<<" OK Fstream FILE "<<endl;
   
   F >> display(X); // not working

   F.close();	
		}*/
int menu(array&A)
{
	int n=1;
	system("cls");
	
	cout<<" \n\n\t\t ***** MENU FILE MANAGEMENT *****"<<endl;
	cout<<" \t\t *                             *"<<endl;
 	cout<<" \t\t *     1. Create array of objects        *"<<endl;
 	cout<<" \t\t *     2. Display array of objects      *"<<endl;
 	cout<<" \t\t *     3. Save file  *"<<endl;
 	cout<<" \t\t *     4. Load file     *"<<endl;
 	cout<<" \t\t *     5. Sum of array     *"<<endl;
 	cout<<" \t\t *     6. Maximum value     *"<<endl;
  	cout<<" \t\t *     ESC. Back               *"<<endl;
  	cout<<" \t\t *                             *"<<endl;
  	cout<<" \t\t *******************************"<<endl;
  		switch(_getch())
 	{
 	   case 49: system("cls"); create(A); system("pause"); 
	   case 50: system("cls"); display(A); system("pause"); 

	   case 27: n=1;
	}
	  return 0;
 }
 		
int main()
{

arrayA[10];


A[0].setN();
menu(*A);
/*
create(*A);
display(*A);
save(*A);

   
 /*  
should be used further for load method. 

   F.open("2021.txt", ios::in  );
     
   if( F.fail() ) cerr<<" Error Fstream FILE "<<endl; 
   else cout<<" OK Fstream FILE "<<endl;
   
   
   F << ;
   F.close();
*/
 
 
 
	return 0;
}
Last edited on
keskiverto (10425)
Your class array contains two int members. Two integers is not what C++ calls "array".


C++ Standard Library offers easy method to locate min and max elements from range:
http://www.cplusplus.com/reference/algorithm/minmax_element/
Last edited on
seeplus (6628)
create an array of "n" elements objects


Based upon using an array of objects - as opposed to an object that holds an array - then consider for a starter:

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#include <fstream>
#include <iostream>
using namespace std;

class Array {
public:
	Array(int val = 0) : value(val) {}
	Array(const Array& Obj) : value(Obj.value) {}

	void setV() { cout << "Enter value: "; cin >> value; }
	void setVA(int val) { value = val; }

	const int getV() const { return value; }

protected:
	int value {};
};

ostream& operator<<(ostream& out, const Array& Obj)
{
	return out << "Array =" << Obj.getV();
}

void create(Array X[], int n)
{
	for (int i = 0; i < n; ++i)
		X[i].setV();
}

void display(const Array X[], int n)
{
	for (int i = 0; i < n; ++i)
		cout << "\nA " << "[" << i << "]" << X[i].getV();
}

int max(const Array X[], int n)
{
	int max = X[0].getV();

	for (int i = 1; i < n; ++i)
		if (max < X[i].getV())
			max = X[i].getV();

		return max;
}

int sum(const Array X[], int n)
{
	int sum {};

	for (int i = 0; i < n; ++i)
		sum += X[i].getV();

	return sum;
}

void menu(Array A[], int n)
{
	//system("cls");
	int opt {};

	do {
		cout << " \n\n\t\t ******* MENU FILE MANAGEMENT *******\n";
		cout << " \t\t *                                  *\n ";
		cout << " \t\t *     1. Create array of objects   *\n";
		cout << " \t\t *     2. Display array of objects  *\n";
		cout << " \t\t *     3. Save file                 *\n";
		cout << " \t\t *     4. Load file                 *\n";
		cout << " \t\t *     5. Sum of array              *\n";
		cout << " \t\t *     6. Maximum value             *\n";
		cout << " \t\t *     0. Exit                      *\n";
		cout << " \t\t *                                  *\n";
		cout << " \t\t ************************************\n";
		cout << " \t\t Enter option number: ";

		cin >> opt;

		switch (opt)
		{
			case 0:
				break;

			case 1:
				//system("cls");
				create(A, n);
				//system("pause");
				break;

			case 2:
				//system("cls");
				display(A, n);
				//system("pause");
				break;

			case 5:
				cout << "The sum of values is " << sum(A, n) << '\n';
				break;

			case 6:
				cout << "The maximum value is " << max(A, n) << '\n';
				break;

			default:
				cout << "Invalid option\n";
		}
	} while (opt != 0);
}

int main()
{
	int N {};

	cout << "Enter N: ";
	cin >> N;

	Array A[10];

	menu(A, N);
}

MaxGreen (115)
@seeplus, thank you so much indeed!
MaxGreen (115)
@seeplus,

hope you can help me again :)

so my functions for saving and loading the FILE are as below : 
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void save(const Array X[], int n){
	
  /*string FN;
  
  cout<<" Enter File name = "; cin >> FN;

  FN+=".txt";
  */
 
  F.open("deep.txt",  ios::out );
   
   if( F.fail() ) cerr<<" Error Fstream FILE "<<endl; 
   else cout<<" OK Fstream FILE "<<endl;
   
   	for (int i = 0; i < n; i++)
		F <<' '<< X[i].getV();
   
   F.close();
    
		}
		
void load(const Array X[], int n)
{

   F.open("deep.txt", ios::in );
  
     if( F.fail() ) cerr<<" Error Fstream FILE "<<endl; 
   else cout<<" OK Fstream FILE "<<endl;
   
  	for (int i = 0; i < n; i++)
		F <<' '<< X[i].getV();
		 
  F.close();
}

It works fine for saving, however when loading it says OK Fstream FILE but I also expect to press on option 2 which is "Display..." and see values which were previous saved into the "deep.txt" FILE, yet values are "0";
seeplus (6628)
In load,
 
 
F <<' '<< X[i].getV();


.getV(), just returns the value - it doesn't set it. You need to use .setVA(). Also you use >> for stream extraction, not << which is for stream insertion. Something like (not tried):

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for (int i = 0; i < n; ++i) {
    int val {};

    F >> val;
    X[i].setVA(val);
}

MaxGreen (115)
@seeplus, I still can't handle it

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#include <fstream>
#include <iostream>
using namespace std;

fstream F;


class Array {
	
public:
	
	void setV() { cout << "Enter value ::: "; cin >> value; }
	
	void setVA(int value) { this->value = value; }

	const int getV() const { return this->value; }
	
	Array(int value = NULL) : value(value) {}
	
	Array(const Array& Obj) : value(Obj.value) {}
	
    ~Array(){}
    
    friend ostream &operator<<(ostream&out, Array&Obj);
    
    friend void display(const Array X[], int n);
    
    friend void create(Array X[], int n);
    
    friend void load(const Array X[], int n);
    
    friend void save (const Array X[], int n);
    
protected:
	
	int value;
	int max(const Array X[], int n)
{
	int max = X[0].getV();

	for (int i = 1; i < n; i++)
		if (max < X[i].getV())
			max = X[i].getV();

		return max;
}

int min(const Array X[], int n)
{
	int min = X[0].getV();

	for (int i = 1; i < n; i++)
		if (min > X[i].getV())
			min = X[i].getV();

		return min;
}


int sum(const Array X[], int n)
{
	int sum = NULL;

	for (int i = 0; i < n; ++i)
		sum += X[i].getV();

	return sum;
}
public: 

void menu(Array A[], int n)
{
	system("cls");
	int option;

	do {
		cout << " \n\n\t\t ******* MENU FILE MANAGEMENT *******\n";
		cout << " \t\t *                                  *\n ";
		cout << " \t\t *     1. Create array of objects   *\n";
		cout << " \t\t *     2. Display array of objects  *\n";
		cout << " \t\t *     3. Save file                 *\n";
		cout << " \t\t *     4. Load file                 *\n";
		cout << " \t\t *     5. Sum of array              *\n";
		cout << " \t\t *     6. Maximum value             *\n";
		cout << " \t\t *     7. Minimum value             *\n";
		cout << " \t\t *     0. Exit                      *\n";
		cout << " \t\t *                                  *\n";
		cout << " \t\t ************************************\n";
		cout << " \n\n\t\t\t Enter option number: ";

		cin >> option;

		switch (option)
		{
			case 0: exit(0);

			case 1: system("cls"); create(A, n); system("pause"); break;

			case 2:	system("cls"); display(A, n); system("pause"); break;
			
			case 3:	system("cls"); save(A, n); system("pause"); break;
			
			case 4:	system("cls"); load(A, n); system("pause"); break;

			case 5: system("cls"); cout << "The sum of values is " << sum(A, n) << '\n'; break;

			case 6: system("cls"); cout << "The maximum value is " << max(A, n) << '\n'; break;
			
			case 7: system("cls"); cout << "The minimum value is " << min(A, n) << '\n'; break;

			default: cout << "Invalid option\n";
		}
	} while (option != 0);
}

};

ostream& operator<<(ostream& out, const Array& Obj)
{
	return out << "Array =" << Obj.getV();
}

istream& operator<<(istream& in, Array& Obj)
{
	cout<< "Enter Array =";
	return in  >> Obj.value;
}


void display(const Array X[], int n)
{
	for (int i = 0; i < n; i++)
		cout << "\nA " << "[" << i << "]" << X[i].getV();
}


void create(Array X[], int n)
{
	
	for (int i = 0; i < n; i++)
		X[i].setV();
}




void save(const Array X[], int n){
 
  F.open("deep.txt",  ios::out );
   
   if( F.fail() ) cerr<<" Error Fstream FILE "<<endl; 
   else cout<<" OK Fstream FILE "<<endl;
   
   	for (int i = 0; i < n; i++)
		F <<' '<< X[i].getV();
   
   F.close();
    
		}
		
void load(const Array X[], int n)
{

   F.open("deep.txt", ios::in );
  
     if( F.fail() ) cerr<<" Error Fstream FILE "<<endl; 
   else cout<<" OK Fstream FILE "<<endl;
   
	for (int i = 0; i < n; i++)
{
	int val[10];
    F >> val;
    X[i].setVA(val);	}
    
     F.close();
}
		 
  F.close();
}

int main()
{
	int N; 
	
	cout << "Enter number of the elements ::: "; cin >> N;
	
	Array A[10],menu;

	menu.menu(A, N);
}


I am trying to overload >> operator as follows 
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istream& operator<<(istream& in, Array& Obj)
{
	cout<< "Enter Array =";
	return in  >> Obj.value;
}


but when i run the code it says that value is protected/private and doesn't have access.
How on earth it can't have access since it is a friend function
seeplus (6628)
istream should overload operator>> not operator<< which is for ostream
MaxGreen (115)
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istream& operator>>(istream& in, Array& Obj)
{
	cout<< "Enter Array =";
	return in  >> Obj.value;
}


my bad, miswritten, but that error still occurs saying ERROR int value is protected and ERROR within context "Obj. [error] value;"
keskiverto (10425)
Because operator>> is a standalone function and tries to access the protected members of class Array. Only members of Array can do that (and classes derived from Array).

Does Array have a public member that writes to Array::value? Yes. Use it:
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istream& operator>>( istream& in, Array& Obj )
{
  cout<< "Enter Array =";
  int x {};
  if ( in >> x ) Obj.setVA( x );
  return in;
}


Note: You have two standalone functions:
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ostream& operator<< ( ostream&, const Array& );
istream& operator>> ( istream&, Array& );

One of them is declared friend of class Array. What does that mean?
MaxGreen (115)
@keskiverto , I was trying to access private/protected zone using a friend function calling it from main, in my specific case overloading the << and >> operators...
thanks for help and explanation guys
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