Creating object in 2D board, using dynamic array

[Kulis18]

I try to create 2D board with random object (#), but the position of "#" do not equal with cords (showing by function show_wall). What I do wrong? My second question is - where I must use delete operator?

  #ifndef BOARD_H
#define BOARD_H

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;



class board
{
    public:
        void size (int n_size) {m_size = n_size; }
        void create_board ();
        void show_wall ();
    private:
        int m_size;
        int m_chance_wall = 80;
        int m_max_wall = 10;
        int* p_wall_x = new int[m_max_wall];
        int* p_wall_y = new int[m_max_wall];

};

void board::show_wall()
{
    for (int i=0; i < m_max_wall; i++)
    {
        cout << "x[" << i << "] = " << *p_wall_x + i << endl;
        cout << "y[" << i << "] = " << *p_wall_y + i << endl;
    }
}

void board::create_board ()
{
    for (int i=0; i < m_size; i++)
    {
        for (int j=0; j < m_size; j++)
        {
            if (rand() % m_chance_wall > 50)
            {
                cout << "[#]";
                *p_wall_x++ = i;
                *p_wall_y++ = j;
                continue;
            }
            cout << "[ ]";
        }
    cout << endl;
    }
}


#endif // BOARD_H
MAIN

#include <iostream>
#include "include\board.h"

// m_ private class
// n_ public class
// p_ pointer

using namespace std;

int main()
{
    srand( time( NULL ) );
    board board_1;
    board_1.size(10);
    board_1.create_board();
    board_1.show_wall();

    return 0;

}