C++ Белый Пояс. Имена и фамилии — 2

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <map>

using namespace std;

class Person {
  public:
    void ChangeFirstName(int year, const string &firstName) {
      firstNames[year] = firstName;
    }

    void ChangeLastName(int year, const string &lastName) {
      lastNames[year] = lastName;
    }

    string GetFullName(int year) const {
      return FirstAndLastNameToText(GetLatestName(year, firstNames),
                                    GetLatestName(year, lastNames));
    }

    string GetFullNameWithHistory(int year) const {
      vector<string> firstNamesChain = GetUniqueChain(year, firstNames);
      vector<string> lastNamesChain = GetUniqueChain(year, lastNames);
      string firstName = GetNameFromUniqueChain(firstNamesChain);
      string lastName = GetNameFromUniqueChain(lastNamesChain);

      return FirstAndLastNameToText(firstName, lastName);
    }

  private:
    map<int, string> firstNames;
    map<int, string> lastNames;

    string FirstAndLastNameToText(const string &firstName, const string &lastName) const {
      if (firstName.empty() && lastName.empty())
        return "Incognito";
      if (firstName.empty())
        return lastName + " with unknown first name";
      if (lastName.empty())
        return firstName + " with unknown last name";
      return firstName + " " + lastName;
    }

    string GetLatestName(const int &year, const map<int, string> &names) const {
      string nameString = "";
      for(const auto &name : names)
        if (name.first > year)
          break;
        else
          nameString = name.second;
      return nameString;
    }

    vector<string> GetUniqueChain(const int &year, const map<int, string> &names) const {
      vector<string> uniqueChain;
      for (const auto &[nameYear, name] : names)
        if (nameYear > year)
          break;
        else if (uniqueChain.empty() || name != uniqueChain.back())
          uniqueChain.push_back(name);
      return uniqueChain;
    }

    string GetNameFromUniqueChain(const vector<string> &uniqueChain) const {
      switch(uniqueChain.size()) {
        case 0:
          return "";
        case 1:
          return uniqueChain[0];
        default:
          string name = uniqueChain.back() + " (" + *(uniqueChain.end() - 2);
          for(int i = uniqueChain.size() - 3; i >= 0; i--)
            name += ", " + uniqueChain[i];
          return name + ")";
      }
    }
};