Seminar2

#include <iostream>
#include <map>
#include <string>
#include <unordered_map>

void try_access_4(const std::unordered_map<int, char>& m) {
  // Оператор [] недоступен.
  std::cout << "Value at 4 = " << m.at(4) << std::endl;
}

int main1() {
  std::unordered_map<int, char> m;
  m.insert({5, 'f'});
  std::cout << "Count 4: " << m.count(4) << std::endl;
  std::cout << "Contains 5: " << (m.contains(5) ? "YES" : "NO") << std::endl;
  const auto i = m.find(5);
  std::cout << (i == m.end() ? "end" : "exists") << std::endl;
  std::cout << i->first << " " << i->second << std::endl;

  m.erase(5);
  std::cout << "Contains 5 after erase: " << (m.contains(5) ? "YES" : "NO") << std::endl;

  // Работа со значением.
  m.insert({5, 'g'});
  std::cout << "Value at 5 = " << m.at(5) << std::endl;
  m.at(5) = 'h';
  std::cout << "Value at 5 after = " << m.at(5) << std::endl;
  // at бросит исключение
  // m.at(4) = 'h';

  std::cout << "Value at 5 = " << m[5] << std::endl;
  try_access_4(m);
  std::cout << "Value at 4 = " << m[4] << std::endl;
  std::cout << "Is zero at 4? " << (m[4] == 0 ? "Zero" : "Non zero") << std::endl;
  return 0;
}

int main2() {
  int n = 0;
  std::cin >> n;
  std::unordered_map<std::string, int> s;
  for (int i = 0; i < n; ++i) {
    std::string str;
    std::cin >> str;
    // Вариант 1
    auto it = s.find(str);
    if (it != s.end()) {
      int value = ++it->second;
      if (value == 2) std::cout << str << std::endl;
    } else {
      s.insert({str, 1});
    }
    // Вариант 2
    // if (++s[str] == 2) std::cout << str << std::endl;
  }
  return 0;
}

int main3() {
  std::map<std::string, int> m;
  m.insert({"aba", 4});
  m.insert({"ac", 5});
  m.insert({"aaaaa", 6});

  auto& [a, b] = *(m.find("ac"));
  std::cout << a << " -> " << b << std::endl;

  for (auto& [key, value] : m) {
    std::cout << key << " -> " << value << std::endl;
  }
  return 0;
}

// Лесенка
int main() {
  int n = 0;
  std::cin >> n;
  if (n <= 1) {
    std::cout << 1 << std::endl;
    return 0;
  }
  int s0 = 1;
  int s1 = 1;
  int s2 = 2;

  for (int i = 0; i < n - 2; ++i) {
    int result = s0 + s1 + s2;
    s0 = s1;
    s1 = s2;
    s2 = result;
    // ??? std::tie(s0, s1, s2) = std::tie(s1, s2, result);
  }
  std::cout << s2 << std::endl;
  return 0;
}