Implement PeopleList

Consider the following PeopleList interface:

typedef std::string InfoType; class PeopleList { public: PeopleList(); // Create an empty In (i.e., one with no InfoType values) bool empty() const; // Return true if the list is empty, otherwise false. int size() const; // Return the number of elements in the linked list. bool add(const std::string& firstName, const std::string& lastName, const InfoType& value); // If the full name (both the first and last name) is not equal to any full name currently // in the list then add it and return true. Elements should be added according to // their last name. Elements with the same last name should be added according to // their first names. Otherwise, make no change to the list and return false // (indicating that the name is already in the list). bool change(const std::string& firstName, const std::string& lastName, const InfoType& value); // If the full name is equal to a full name currently in the list, then make that full // name no longer map to the value it currently maps to, but instead map to // the value of the third parameter; return true in this case. // Otherwise, make no change to the list and return false. bool addOrChange(const std::string& firstName, const std::string& lastName, const InfoType& value); // If full name is equal to a name currently in the list, then make that full name no // longer map to the value it currently maps to, but instead map to // the value of the third parameter; return true in this case. // If the full name is not equal to any full name currently in the list then add it // and return true. In fact this function always returns true. bool remove(const std::string& firstName, cont std::string& lastName); // If the full name is equal to a full name currently in the list, remove the // full name and value from the list and return true. Otherwise, make // no change to the list and return false. bool contains(const std::string& firstName, const std::string& lastName) const; // Return true if the full name is equal to a full name currently in the list, otherwise // false. bool lookup(const std::string& firstName, const std::string& lastName, InfoType& value) const; // If the full name is equal to a full name currently in the list, set value to the // value in the list that that full name maps to, and return true. Otherwise, // make no change to the value parameter of this function and return // false. bool get(int i, std::string& firstName, std::string& lastName, InfoType& value) const; // If 0 <= i < size(), copy into firstName, lastName and value parameters the // corresponding information of the element at position i in the list and return // true. Otherwise, leave the parameters unchanged and return false. // (See below for details about this function.) void swap(PeopleList& other); // Exchange the contents of this list with the other one. };