course1_week3_challenge.cpp

// A class called Pair has already been declared, but the constructors have not been implemented yet. Pair has two public member variables:

// int *pa,*pb;

// These two "pointers to int" are intended to point to heap memory locations that store integers. The remainder of the Pair class expects the 
// following functionality.

// A single constructor Pair(int a, int b): This should set up pa and pb to point to newly allocated memory locations on the heap. The integers 
// at those memory locations should be assigned values according to the constructor's integer arguments a and b.
// A copy constructor Pair(const Pair& other): This takes as its argument a read-only reference to another Pair. It should set up the newly 
// constructed Pair as a "deep copy," that is, it should create a new Pair that is equivalent to the other Pair based on dereferenced values but 
// does not reuse any of the same memory locations. In other words, the copy constructor should set up its own instance's member variables pa and 
// pb to point to newly allocated memory locations for integers on the heap; those memory locations must be new, not the same locations pointed to 
// by the other Pair, but the integers at these new locations should be assigned values according to the integers that the other Pair is pointing to.
// A destructor ~Pair() that de-allocates all of the the heap memory that had previously been allocated for this Pair's members.
// The types of these member functions have already been declared in the declaration of Pair. Now you need to provide the implementation of each of 
// these three member functions.

/* Class Pair has already been declared
 * as shown in the following comments:
 *
 * class Pair {
 * public:
 *   int *pa,*pb;
 *   Pair(int, int);
 *   Pair(const Pair &);
 *  ~Pair();
 * };
 *
 * Implement its member functions below.
 */
 Pair::Pair(int a, int b) {
    pa = new int;
    pb = new int;
    *pa = a;
    *pb = b;
  };
  Pair::Pair(const Pair & obj) {
    pa = new int;
    pb = new int;
    *pa = *obj.pa;
    *pb = *obj.pb;
  };
  Pair::~Pair() {
    delete pa; pa = nullptr;
    delete pb; pb = nullptr;
  };

 
 
 
 /* Here is a main() function you can use
  * to check your implementation of the
  * class Pair member functions.
  */
  
int main() {
  Pair p(15,16);
  Pair q(p);
  Pair *hp = new Pair(23,42);
  delete hp;
  
  std::cout << "If this message is printed,"
    << " at least the program hasn't crashed yet!\n"
    << "But you may want to print other diagnostic messages too." << std::endl;
  return 0;
}