деструктор

class A{}
class B{
A *a;
B(){
a=new A();
}
}

delete a;

class A{
  A*a;
  ~A(){
    a->~A();//надо ли это?
    delete a;
  }
}

A ****a;

#include <iostream>
using std::cout;
 
int main()
{
    int ***ptr = NULL;
 
    ptr = new int **[3];
    cout << ptr << " was created\n";
 
    for (int i = 0; i < 3; ++i) {
        ptr[i] = new int *[3];
        cout << ptr[i] << " was created\n";
 
        for (int j = 0; j < 3; ++j) {
            ptr[i][j] = new int;
            cout << ptr[i][j] << " was created\n";
        }
    }
 
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            cout << ptr[i][j] << " was deleted\n";
            delete ptr[i][j];
        }
 
        cout << ptr[i] << " was deleted\n";
        delete[] ptr[i];
    }
 
    cout << ptr << " was deleted\n";
    delete[] ptr;
}

#include <iostream>
using std::cout;
 
class Object
{
public:
    Object() {
        ptr = new int;
        cout << ptr << " was created\n";
    }
 
    ~Object() {
        cout << ptr << " was deleted\n";
        delete ptr;
    }
 
private:
    int *ptr;
};
 
int main()
{
    Object *objects = new Object[2];
    cout << objects << " was created\n";
 
    cout << objects << " was deleted\n";
    delete[] objects;
}

int** a = new int*[10];
for(int i = 0; i < 10; i++)
a[i] = new int[15];
...
//работа с матрицей
...
for(int i = 0; i < 10; i++)
delete [] a[i];
delete a;

class A{
public:
A*a;
~A(){delete a;}
}
void Main(){
   A *a=new A();
   a->a=new A();
   a->a->a=new A();
   a->a->a->a=new A();
   a->a->a->a->a=new A();
   delete a;
}

if(a!=NULL) delete a;

class A {
public:
    A *a;
 
    A() {
        a = NULL;
    }
 
    ~A() {
        if (a != NULL)
            delete a;
    }
};
 
int main() {
    A *a = new A();
    a->a = new A();
    a->a->a = new A();
 
    delete a;
}