Did I use friend class correctly?

[nataliay]

#include <iostream>
using namespace std;
class vector
{
private:
	int size;
	int *p;
	friend class multiply;
public:
	vector(int a)
	{
		size = a;
		p = new int[a];
	}
	int getsize()
	{
		return size;
	}
	void input()
	{
		for (int i = 0; i < size; i++)
		{
			int x;
			cout << "Enter values" << endl;
			cin >> x;
			p[i] = x;
		}
	}
	void output()
	{
		for (int i = 0; i < size; i++)
		{
			cout << p[i] << " ";
		}
		cout << endl;
	}
	int getelement(int i)
	{
		return p[i];
	}
};
class matrix
{
private:
	int row;
	int col;
	int **r;
	friend class multiply;
public:
	matrix(int s, int a)
	{
		row = s;
		col = a;
		r = new int*[s];
		for (int i = 0; i < s; i++)
		{
			r[i] = new int[a];
		}
	}
	int getrow()
	{
		return row;
	}
	int getcol()
	{
		return col;
	}
	void input()
	{
		for (int i = 0; i < row; i++)
		{
			for (int j = 0; j < col; j++)
			{
				int x;
				cout << "Enter values for matrix" << endl;
				cin >> x;
				r[i][j] = x;
			}
		}
	}
	void output()
	{

		for (int i = 0; i < row; i++)
		{
			for (int j = 0; j < col; j++)
			{
				cout << r[i][j] << " ";
			}
			cout << endl;
		}
	}
	int getelement(int i, int j)
	{
		return r[i][j];
	}
};
class multiply
{
private:
	int r;
	int c;
	int **a;
public:
	multiply(int s, int a)
	{
		r = s;
		c = a;
		a = new int*[s];
		for (int i = 0; i < s; i++)
		{
			a[i] = new int[a];
		}
	}
	void input()
	{
		for (int i = 0; i < r; i++)
		{
			for (int j = 0; j < c; j++)
			{
				a[i][j] = 0;
			}
		}
	}
	for (int i = 0; i < matrix.r; i++)
	{
		if (matrix.row != vector.p)
		{
			cout << "Can't be multiplied" << endl;
		}
		else
		{
			for (int j = 0; j < matrix.col; j++)
			{
				for (int k = 0; k < matrix.row; k++)
				{
					a[i][k] += matrix.r[i][j] * vector.p[k];
				}
			}
		}
	}
};
void main()
{
	int s, r;
	cout << "Enter size" << endl;
	cin >> s;
	vector c(s);
	c.input();
	c.output();
	cout << "Your element is:" << c.getelement(5) << endl;
	cout << "Enter number of rows" << endl << ;
	cin >> r;
	matrix b(r, 1);
	b.input();
	b.output();
	cout << "Your element is:" << b.getelement(1, 0) << endl;

}

This code is supposed to multiply the vector by the matrix, I have to use friend class and I'm not exactly sure I used it correctly. Can someone help me? And how do I call it in the main function?? Please, I need help with it

[MikeyBoy]

In lines 125 to 137, you're using matrix like it's the name of an object, but I don't see any object with that name defined anywhere.

Did you intend for there to be an instance of the class matrix in there somewhere?

In fact... lines 125 - 141 look as though they're not inside any method or function. The input() function ends at 124, and then there's a "for" statement immediately afterwards. You can't do that.

[nataliay]

I didn't want to use it as an object, I meant that the code should take row from class matrix and use it in class multiply (since there is a friend class)
But again, I'm not sure about how friend class works and how do I use it.
Do you know how can I rewrite my code using friend class?

[MikeyBoy]

Making multiply a friend class of matrix, just means that methods of multiply can access the private members of matrix objects. A method of multiply will still need to have a matrix object to operate on, just as it would if it wasn't a friend class and was having to use the public interface of matrix instead.