ass_containers.cc

#include <iostream>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>

struct Person {
  std::string first_name;
  std::string last_name;
  int age;
};

std::ostream& operator<<(std::ostream& stream, const Person p) {
  stream << p.first_name << " " << p.last_name << " (" << p.age << ")";

  return stream;
}

struct Student {
  size_t id;
  Person person;
};

// required by set
bool operator<(const Student lhv, const Student rhv) {
  return lhv.id < rhv.id;
}

// required by unordered_set
bool operator==(const Student lhv, const Student rhv) {
  return lhv.id == rhv.id;
}

// required by unoredered_set
namespace std {

template <> struct hash<Student> {
  size_t operator()(const Student& student) const {
      std::hash<size_t> hash;
      return hash(student.id);
  }
};

}

int main() {
  std::map<size_t, Person> people1 = {
    {1001, {"Alice", "Cooper", 69}},
    {1021, {"Bodo", "Kaiser", 23}},
    {1221, {"Angela", "Merkel", 70}}
  };

  std::cout << "map:" << std::endl;
  for (auto const& [id, person] : people1) {
    std::cout << person << std::endl;
  }

  std::unordered_map<size_t, Person> people2 = {
    {1001, {"Alice", "Cooper", 69}},
    {1021, {"Bodo", "Kaiser", 23}},
    {1221, {"Angela", "Merkel", 70}}
  };

  std::cout << "unordered_map:" << std::endl;
  for (auto const& [id, person] : people2) {
    std::cout << person << std::endl;
  }

  std::set<Student> students1 = {
    {1001, {"Homer", "Simpson", 69}},
    {1021, {"Carl", "Johnson", 23}},
    {1221, {"Nico", "Bellic", 70}}
  };

  std::cout << "set:" << std::endl;
  for (auto const& student : students1) {
    std::cout << student.person << std::endl;
  }

  std::unordered_set<Student> students2 = {
    {1001, {"Homer", "Simpson", 69}},
    {1021, {"Carl", "Johnson", 23}},
    {1221, {"Nico", "Bellic", 70}}
  };

  std::cout << "unordered_set:" << std::endl;
  for (auto const& student : students2) {
    std::cout << student.person << std::endl;
  }
}