In C++ #ifndef PERSON_H #define PERSON_H #include  using namespace std; class Person { string name; Person * best_friend; int popularity; public: Person(): name(""), best_friend(0), popularity(0) { } Person(string n): name(n), best_friend(0), popularity(0) { } string get_name(); string get_best_friend(); int get_popularity(); void set_best_friend(Person *); }; #endif 

 #include "Person.h" string Person::get_name() { return name; } string Person::get_best_friend() { if (best_friend != 0) // check for null pointer return best_friend->name; else return ""; } int Person::get_popularity() { return popularity; } void Person::set_best_friend(Person * bf) { best_friend = bf; (bf->popularity)++; } 

 #include  #include  // for setw #include  // for ifstream #include  #include  #include "Person.h" using namespace std; main() { string name; vector people; // vector of pointers to objects of type Person Person * person_pointer; ifstream in; in.open("names"); if (!in.is_open()) { cout << "Couldn't open 'names' file. "; return 1; } in >> name; while (!in.eof()) { person_pointer = new Person(name); people.push_back(person_pointer); // no check for duplicate names in >> name; } in.close(); int i, j; // for each person prompt for a best friend name for (i = 0; i < people.size(); i++) { cout << "Who is " << people[i]->get_name() << "'s best friend? "; cin >> name; // search for best friend for (j = 0; j < people.size(); j++) if (people[j]->get_name() == name) break; if (j < people.size()) // found a best friend people[i]->set_best_friend(people[j]); else cout << "Couldn't find best friend " << name << endl; } // list of name, best friend, and popularity count for (i = 0; i < people.size(); i++) { person_pointer = people[i]; cout << left << setw(10) << person_pointer->get_name(); cout << left << setw(10) << person_pointer->get_best_friend(); cout << right << setw(2) << person_pointer->get_popularity() << endl; } // clean up for (i = 0; i < people.size(); i++) delete people[i]; }

4. Modify the program to prevent duplicate names being inserted in the vector and modify the program to prompt the user for another name if best friend is not found.