cs440-assignment2/Map.hpp

#ifndef _POWELL_CS440
#define _POWELL_CS440
#include <algorithm>
// uncomment on submission/performance test
// #define NDEBUG
#include <cassert>
#include <memory>
#include <optional>
#include <stdexcept>
#include <utility>
namespace cs440 {
// universal type defs here
namespace {
enum class Direction { Left, Right };
Direction operator!(Direction dir) {
  switch (dir) {
  case Direction::Left:
    return Direction::Right;
  case Direction::Right:
    return Direction::Left;
  default:
    assert(false);
  }
}
enum class Color { Red, Black };
} // namespace
template <typename Key_T, typename Mapped_T> class Map {
  // Type definitions here
  using ValueType = std::pair<const Key_T, Mapped_T>;
  using internal_ValueType = std::pair<Key_T, Mapped_T>;

  struct Node {
    int valid = 0x13371337;
    Node *parent = nullptr;
    std::unique_ptr<internal_ValueType> val;
    std::unique_ptr<Node> left;
    std::unique_ptr<Node> right;
    Color color;
    Node *prev;
    Node *next;
    Map *map;
    Node(internal_ValueType val, Map *map)
        : parent{nullptr}, val{new internal_ValueType{val}}, left{}, right{},
          color{Color::Red}, prev{nullptr}, next{nullptr}, map{map} {}
    Node(const Node &rhs)
        : parent{nullptr},
          val{rhs.val ? new internal_ValueType{*rhs.val} : nullptr},
          left{rhs.left ? std::make_unique<Node>(*rhs.left) : nullptr},
          right{rhs.right ? std::make_unique<Node>(*rhs.right) : nullptr},
          color{rhs.color}, prev{nullptr}, next{nullptr}, map{rhs.map} {
      this->valid = 0x13371337;

      if (this->left) {
        this->left->parent = this;
      }
      if (this->right) {
        this->right->parent = this;
      }

      this->next = rhs.next;
      this->prev = rhs.prev;
    }
    Node(Node &&rhs)
        : parent{nullptr}, val{std::move(rhs.val)}, left{std::move(rhs.left)},
          right{std::move(rhs.right)}, color{rhs.color}, prev{nullptr},
          next{nullptr}, map{rhs.map} {

      rhs.valid = 0;
      this->valid = 0x13371337;

      if (this->left) {
        this->left->parent = this;
      }
      if (this->right) {
        this->right->parent = this;
      }

      this->next = rhs.next;
      this->prev = rhs.prev;
    }
    ~Node() {}
    Node &operator=(const Node &rhs) {
      // retain parent as is, common case is the copy or move is happening due
      // to a rotation where parent can get wonky
      // this->parent

      this->val =
          rhs.val ? std::unique_ptr<internal_ValueType>{new internal_ValueType{
                        *rhs.val}}
                  : nullptr;
      this->left = rhs.left ? std::make_unique<Node>(*rhs.left) : nullptr;
      this->right = rhs.right ? std::make_unique<Node>(*rhs.right) : nullptr;
      this->color = rhs.color;
      this->valid = 0x13371337;

      if (this->left) {
        this->left->parent = this;
        this->left->restore_ordering();
      }
      if (this->right) {
        this->right->parent = this;
        this->right->restore_ordering();
      }
      this->restore_ordering();
      this->map = rhs.map;
      return *this;
    }
    Node &operator=(Node &&rhs) {
      // retain parent as is, common case is the copy or move is happening due
      // to a rotation where parent can get wonky
      // this->parent
      this->val = std::move(rhs.val);
      this->left = std::move(rhs.left);
      this->right = std::move(rhs.right);
      this->color = rhs.color;
      this->valid = 0x13371337;
      rhs.valid = 0;
      if (this->left) {
        this->left->parent = this;
        this->left->restore_ordering();
      }
      if (this->right) {
        this->right->parent = this;
        this->right->restore_ordering();
      }
      this->restore_ordering();
      this->map = rhs.map;
      return *this;
    }
    Node *child(Direction dir) {
      switch (dir) {
      case Direction::Left:
        return this->left.get();
      case Direction::Right:
        return this->right.get();
      default:
        assert(false);
      }
    }
    Node const *child(Direction dir) const {
      switch (dir) {
      case Direction::Left:
        return this->left.get();
      case Direction::Right:
        return this->right.get();
      default:
        assert(false);
      }
    }
    std::unique_ptr<Node> uchild(Direction dir) {
      switch (dir) {
      case Direction::Left:
        return std::move(this->left);
      case Direction::Right:
        return std::move(this->right);
      default:
        assert(false);
      }
    }
    std::unique_ptr<Node> uchild(Node *child) {
      return this->uchild(this->which_child(child));
    }
    std::unique_ptr<Node> &set_child(Direction dir,
                                     std::unique_ptr<Node> new_child) {

      if (new_child) {
        new_child->parent = this;
      }
      switch (dir) {
      case Direction::Left:

        this->left = std::move(new_child);
        if (this->left) {
          this->left->parent = this;
        }
        return this->left;
      case Direction::Right:
        this->right = std::move(new_child);
        if (this->right) {
          this->right->parent = this;
        }
        return this->right;
      default:
        assert(false);
      }
    }
    Direction which_child(Node *n) {
      if (this->left.get() == n) {
        return Direction::Left;
      }
      if (this->right.get() == n) {
        return Direction::Right;
      }
      assert(false);
    }
    void erase_child(Node *n) { this->erase_child(this->which_child(n)); }
    void erase_child(Direction dir) {
      bool minmax = this->child(dir) == this->map->min ||
                    this->child(dir) == this->map->max;
      // bringing ownership to this function scope so Deleter gets called at end
      // of function and we can do reordering things
      std::unique_ptr<Node> dropping;
      switch (dir) {
      case Direction::Right:
        dropping = std::move(this->right);
        break;
      case Direction::Left:
        dropping = std::move(this->left);
        break;
      default:
        assert(false);
      }

      // intuitively should be correct but might need to do restore ordering on
      // both instead
      if (dropping->prev != nullptr) {
        dropping->prev->next = dropping->next;
      }

      if (dropping->next != nullptr) {
        dropping->next->prev = dropping->prev;
      }

      if (minmax) {
        switch (dir) {
        case Direction::Left:
          this->map->min = this;
          break;
        case Direction::Right:
          this->map->max = this;
          break;
          assert(false);
        }
      }
    }
    void restore_ordering() {
      this->prev = this->calc_pred();
      this->next = this->calc_succ();
      if (this->prev) {
        this->prev->next = this;
      }
      if (this->next) {
        this->next->prev = this;
      }
    }
    Node *calc_pred() {
      if (this->left) {
        Node *ret = this->left.get();
        while (ret->right) {
          ret = ret->right.get();
        }
        return ret;
      } else {
        Node *ret = this->parent;
        Node *prev_ret = this;
        while (ret && ret->which_child(prev_ret) != Direction::Right) {
          prev_ret = ret;
          ret = prev_ret->parent;
        }
        return ret;
      }
    }
    Node *calc_succ() {
      if (this->right) {
        Node *ret = this->right.get();
        while (ret->left) {
          ret = ret->left.get();
        }
        return ret;
      } else {
        Node *ret = this->parent;
        Node *prev_ret = this;
        while (ret && ret->which_child(prev_ret) != Direction::Left) {
          prev_ret = ret;
          ret = prev_ret->parent;
        }
        return ret;
      }
    }
    void rotate(Direction dir) {

      // cannot rotate nullptr
      assert(this != nullptr);

      // we can't be root for this rotate operation
      assert(this->parent != nullptr);

      // if we're missing the child on the opposite direction this is an invalid
      // rotation
      assert(this->child(!dir));

      // gotta pull outselves out of parent to avoid accidentally overwriting
      // outselves
      std::unique_ptr<Node> self = this->parent->uchild(!dir);

      // make sure this is actually us
      assert(self.get() == this);

      // make our former position the position of the relevant child
      this->parent->set_child(!dir, this->uchild(!dir));

      // steal our former child's child
      this->set_child(!dir, this->parent->child(!dir)->uchild(dir));

      // make ourselves our former child's child
      this->parent->child(!dir)->set_child(dir, std::move(self));
    }
    // Referencing
    // https://en.wikipedia.org/wiki/Red%E2%80%93black_tree#Notes_to_the_insert_diagrams
    void restore_red_black_insert(Direction dir) {
      Node *self = this;

      // infinite loop for case 2's sake, if tail recursion optimization was
      // guaranteed I'd use tail recursion
      while (true) {
        Node *parent = self->parent;
        // we're root, no-op (case 3)
        if (!parent) {
          self->color = Color::Black;
          return;
        }

        // if this is violated it's a bug
        assert(parent->child(dir) == self);

        // parent is black so no violation no-op (case 1)
        if (parent->color == Color::Black) {
          return;
        }

        Node *grandparent = parent->parent;

        // parent is root (case 4)
        if (!grandparent) {
          parent->color = Color::Black;
          return;
        }

        // table showing transforms on wikipedia doesn't have this so if it
        // happens it's probably a bug
        assert(grandparent->color == Color::Black);

        Node *uncle = grandparent->child(!grandparent->which_child(parent));
        if (uncle == nullptr || uncle->color == Color::Black) {
          if (parent->which_child(self) != grandparent->which_child(parent)) {
            // we're an inner child
            // case 5
            parent->rotate(dir);
            self = parent;
            parent = self->parent;
          }
          // case 6

          // recolor first so we aren't recoloring a dropped reference or smth
          parent->color = Color::Black;
          grandparent->color = Color::Red;
          if (grandparent->parent == nullptr) {
            map->rotate_root(!dir);
          } else {
            grandparent->rotate(!dir);
          }
          return;
        }

        // case 2 (by process of elimination)
        parent->color = Color::Black;
        uncle->color = Color::Black;
        grandparent->color = Color::Red;
        self = grandparent;
      }
    }
  };

  // data needed for implementation
  std::optional<Node> root;
  std::size_t _size;
  Node *min;
  Node *max;

public:
  friend Node;
  class ConstIterator;
  class ReverseIterator;
  // public type definitions
  class Iterator {
    Node *underlying;
    Node *store;
    Iterator(Node *ptr, Node *potential = nullptr)
        : underlying{ptr}, store{potential} {}

  public:
    friend Map;
    friend ConstIterator;
    friend ReverseIterator;
    Iterator() = delete;
    Iterator(const Iterator &rhs) = default;
    Iterator &operator=(const Iterator &) = default;
    ~Iterator() = default;
    // precrement
    Iterator &operator++() {
      if (this->underlying == nullptr) {
        this->underlying = this->store;
        this->store = nullptr;
        return *this;
      }
      if (this->underlying->next == nullptr) {
        this->store = this->underlying;
      }
      this->underlying = this->underlying->next;
      return *this;
    }
    // postcrement
    Iterator operator++(int) {
      auto copy = *this;
      this->operator++();
      return copy;
    }

    // precrement
    Iterator &operator--() {
      if (this->underlying == nullptr) {
        this->underlying = this->store;
        this->store = nullptr;
        return *this;
      }
      if (this->underlying->prev == nullptr) {
        this->store = this->underlying;
      }
      this->underlying = this->underlying->prev;
      return *this;
    }
    // postcrement
    Iterator operator--(int) {
      auto copy = *this;
      this->operator--();
      return copy;
    }

    ValueType &operator*() const {
      ValueType *ret = (ValueType *)(&this->underlying->val);
      return *ret;
    }
    ValueType *operator->() const { return &this->operator*(); }
    friend bool operator==(const Iterator &lhs, const Iterator &rhs) {
      return lhs.underlying == rhs.underlying;
    }
    friend bool operator!=(const Iterator &lhs, const Iterator &rhs) {
      return !(lhs == rhs);
    }
  };
  class ConstIterator {
    Iterator underlying;

  public:
    friend Map;
    ConstIterator() = delete;
    ConstIterator(const Iterator &underlying) : underlying{underlying} {}
    ConstIterator(const ConstIterator &rhs) = default;
    ConstIterator &operator=(const ConstIterator &) = default;
    ~ConstIterator() = default;
    ConstIterator &operator++() {
      ++underlying;
      return *this;
    }
    ConstIterator operator++(int) {
      auto copy = *this;
      this->operator++();
      return copy;
    }
    ConstIterator &operator--() {
      --underlying;
      return *this;
    }
    ConstIterator operator--(int) {
      auto copy = *this;
      this->operator--();
      return copy;
    }
    const ValueType &operator*() const { return this->underlying.operator*(); }
    const ValueType *operator->() const { return &this->operator*(); }

    friend bool operator==(const ConstIterator &lhs, const ConstIterator &rhs) {
      return lhs.underlying == rhs.underlying;
    }
    friend bool operator!=(const ConstIterator &lhs, const ConstIterator &rhs) {
      return !(lhs == rhs);
    }
    friend bool operator==(const Iterator &lhs, const ConstIterator &rhs) {
      return lhs == rhs.underlying;
    }
    friend bool operator!=(const Iterator &lhs, const ConstIterator &rhs) {
      return !(lhs == rhs);
    }
    friend bool operator==(const ConstIterator &lhs, const Iterator &rhs) {
      return lhs.underlying == rhs;
    }
    friend bool operator!=(const ConstIterator &lhs, const Iterator &rhs) {
      return !(lhs == rhs);
    }
  };
  class ReverseIterator {
    Iterator underlying;
    ReverseIterator(const Iterator &underlying) : underlying{underlying} {}

  public:
    friend Map;
    ReverseIterator() = delete;
    ReverseIterator(const ReverseIterator &) = default;
    ~ReverseIterator() = default;
    ReverseIterator &operator=(const ReverseIterator &) = default;
    ReverseIterator &operator++() {
      --underlying;
      return *this;
    }
    ReverseIterator operator++(int) {
      auto copy = *this;
      this->operator++();
      return copy;
    }
    ReverseIterator &operator--() {
      ++underlying;
      return *this;
    }
    ReverseIterator operator--(int) {
      auto copy = *this;
      this->operator++();
      return copy;
    }
    const ValueType &operator*() const { return this->underlying.operator*(); }
    const ValueType *operator->() const { return &this->operator*(); }
  };

  Map() : root{}, _size{0} {}
  Map(const Map &rhs) : root{rhs.root}, _size{rhs._size} {
    this->min = &this->root.value();
    this->max = &this->root.value();
    while (min->left) {
      min = min->left.get();
    }
    while (min->right) {
      min = min->left.get();
    }
  }
  Map(Map &&rhs) : root{std::move(rhs.root)}, _size{rhs._size} {
    this->min = &this->root.value();
    this->max = &this->root.value();
    while (min->left) {
      min = min->left.get();
    }
    while (min->right) {
      min = min->left.get();
    }
  }
  Map &operator=(const Map &rhs) {
    this->root = rhs.root;
    this->_size = rhs._size;
    return *this;
  }
  Map &operator=(Map &&rhs) {
    this->root = std::move(rhs.root);
    this->_size = rhs._size;
    return *this;
  }
  Map(std::initializer_list<std::pair<const Key_T, Mapped_T>> items) : Map{} {
    this->insert(items.begin(), items.end());
  }
  void check() {
    assert(!this->root || this->root.value().color == Color::Black);
  }
  std::size_t size() const { return this->_size; }
  bool empty() const { return this->size() == 0; }

private:
  // private helpers
  void rotate_root(Direction dir) {
    assert(root.has_value());

    std::unique_ptr<Node> new_root = root.value().uchild(!dir);
    // can't make null the new root
    assert(new_root);

    std::unique_ptr<Node> old_root =
        std::make_unique<Node>(std::move(root.value()));

    root.value() = std::move(*new_root.release());

    old_root->set_child(!dir, root.value().uchild(dir));

    if (old_root->left) {
      old_root->left->parent = old_root.get();
    }
    if (old_root->right) {
      old_root->right->parent = old_root.get();
    }
    if (old_root->next) {
      old_root->next->prev = old_root.get();
    }
    if (old_root->prev) {
      old_root->prev->next = old_root.get();
    }

    root.value().set_child(dir, std::move(old_root));
    root.value().child(dir)->restore_ordering();

    if (root.value().left) {
      root.value().left->parent = &root.value();
      if (min == &root.value()) {
        min = root.value().left.get();
      }
    }
    if (root.value().right) {
      root.value().right->parent = &root.value();
      if (max == &root.value()) {
        max = root.value().right.get();
      }
    }
  }
  template <bool trace = false>
  std::pair<Node const *, Direction> locate(const Key_T &key) const {
    Node const *ret_parent;
    Direction ret_dir;
    // map is empty
    if (!this->root.has_value()) {
      return std::make_pair(nullptr, ret_dir);
    }
    // value is in root
    if (this->root.value().val->first == key) {

      return std::make_pair(nullptr, ret_dir);
    }
    ret_parent = &this->root.value();
    if (key < ret_parent->val->first) {
      ret_dir = Direction::Left;
    } else {
      ret_dir = Direction::Right;
    }
    while (ret_parent->child(ret_dir) &&
           !(ret_parent->child(ret_dir)->val->first == key)) {
      ret_parent = ret_parent->child(ret_dir);
      if (key < ret_parent->val->first) {
        ret_dir = Direction::Left;
      } else {
        ret_dir = Direction::Right;
      }
    }
    return std::make_pair(ret_parent, ret_dir);
  }
  void hard_erase(Node *n) {
    assert(n->parent);
    Node *parent = n->parent;
    Direction dir = parent->which_child(n);
    parent->erase_child(n);
    goto skip;
    while (true) {
      parent = n->parent;
      if (parent == nullptr) {
        // we're at root we're done (case 1)
        return;
      }
      dir = parent->which_child(n);
    skip:
      Color par_color = parent->color;

      Node *sibling = parent->child(!dir);
      Color sibling_color = sibling ? sibling->color : Color::Black;

      Node *close = sibling ? sibling->child(dir) : nullptr;
      Node *distant = sibling ? sibling->child(!dir) : nullptr;

      Color close_color = close ? close->color : Color::Black;
      Color distant_color = distant ? distant->color : Color::Black;

#define redcheck(v) if ((v) == Color::Red)
      // it kinda sucks but I think that goto is genuinely the best solution
      // here, making methods for cases 4,5 and 6 is a lot of unneeded
      // bookkeeping
      redcheck(sibling_color) {
        // case 3
        if (parent->parent != nullptr) {
          parent->rotate(dir);
        } else {
          parent->map->rotate_root(dir);
        }
        parent->color = Color::Red;
        sibling->color = Color::Black;
        sibling = close;

        distant = sibling->child(!dir);
        if (distant != nullptr && distant->color == Color::Red) {
          goto case_6;
        }
        close = sibling->child(dir);
        if (close != nullptr && close->color == Color::Red) {
          goto case_5;
        }
        goto case_4;
      }
      else redcheck(close_color) {
      // case 5
      case_5:
        assert(sibling);
        assert(close);
        sibling->rotate(!dir);
        sibling->color = Color::Red;
        close->color = Color::Black;
        distant = sibling;
        sibling = close;
        goto case_6;
      }
      else redcheck(distant_color) {
        // case 6
      case_6:
        assert(parent);
        assert(sibling);
        assert(distant);
        if (parent->parent != nullptr) {
          parent->rotate(dir);
        } else {
          parent->map->rotate_root(dir);
        }
        Color tmp = parent->color;
        sibling->color = tmp;
        parent->color = Color::Black;
        distant->color = Color::Black;
        return;
      }
      else redcheck(par_color) {
      // case 4
      case_4:
        assert(sibling);
        sibling->color = Color::Red;
        parent->color = Color::Black;
        return;
      }
      else {
        // case 2
        assert(sibling);
        sibling->color = Color::Red;
        n = parent;
        continue;
      }
    }
  }
  bool core_erase(Node *erasing) {
    Color c = erasing->color;
    // 2 children
    if (erasing->left && erasing->right) {
      Node *succ = erasing->next;
      erasing->val = std::move(succ->val);
      this->core_erase(succ);
    }
    // 1 child
    else if (erasing->left) {
      *erasing = std::move(*erasing->left.release());
      if (erasing->prev != nullptr) {
        erasing->prev->next = erasing;
      }
      if (erasing->next != nullptr) {
        erasing->next->prev = erasing;
      }
      erasing->color = c;
      return true;
    } else if (erasing->right) {
      *erasing = std::move(*erasing->right.release());
      if (erasing->prev != nullptr) {
        erasing->prev->next = erasing;
      }
      if (erasing->next != nullptr) {
        erasing->next->prev = erasing;
      }
      erasing->color = c;
      return true;
    }
    //  no children and root
    else if (erasing->parent == nullptr) {
      erasing->map->root = std::nullopt;
    }
    //  no children and red
    else if (erasing->color == Color::Red) {
      erasing->parent->erase_child(erasing);
    }
    // no children and black
    else {
      hard_erase(erasing);
    }
    return false;
  }

public:
  // baseline find using locate
  Iterator find(const Key_T &key) {
    auto [parent, dir] = locate(key);
    if (parent == nullptr) {
      if (this->root.has_value()) {
        if (this->root.value().val->first == key) {
          return Iterator{&this->root.value()};
        }
      }
      return this->end();
    }
    if (parent->child(dir) != nullptr) {
      return Iterator{const_cast<Node *>(parent->child(dir)), nullptr};
    }
    return this->end();
  }
  ConstIterator find(const Key_T &key) const {
    auto [parent, dir] = locate(key);
    if (parent == nullptr) {
      if (this->root.has_value()) {
        if (this->root.value().val->first == key) {
          return Iterator{const_cast<Node *>(&this->root.value())};
        }
      }
      return this->end();
    }
    if (parent->child(dir) != nullptr) {
      return Iterator{const_cast<Node *>(parent->child(dir)), nullptr};
    }
    return this->end();
  }
  // baseline modification operations
  std::pair<Iterator, bool> insert(const ValueType &val) {
    // for convenience
    auto &[key, map] = val;

    auto [parent, dir] = locate(key);
    // located root node
    if (parent == nullptr) {
      if (this->root.has_value()) {
        return std::make_pair(Iterator{&root.value()}, false);
      } else {
        this->root = Node{val, this};
        this->root.value().color = Color::Black;
        this->min = &this->root.value();
        this->max = &this->root.value();
        this->_size++;
        return std::make_pair(Iterator{&root.value()}, true);
      }
    }

    // non-root node
    if (parent->child(dir)) {
      // node already present
      return std::make_pair(Iterator{const_cast<Node *>(parent->child(dir))},
                            false);
    }

    // need to insert non-root node
    Map *m = const_cast<Map *>(this);
    Node *new_node = const_cast<Node *>(parent)
                         ->set_child(dir, std::make_unique<Node>(Node{val, m}))
                         .get();
    new_node->restore_red_black_insert(dir);

    new_node->restore_ordering();
    if (this->min == parent && dir == Direction::Left) {
      this->min = new_node;
    }
    if (this->max == parent && dir == Direction::Right) {
      this->max = new_node;
    }
    this->_size++;
    return std::make_pair(Iterator{new_node}, true);
  }
  void erase(Iterator pos) {
    if (pos.underlying == nullptr) {
      return;
    }
    this->_size--;

    Node *before = pos.underlying->prev;
    Node *after = pos.underlying->next;
    if (core_erase(pos.underlying)) {
      pos.underlying->restore_ordering();
    } else {
      if (before != nullptr && before->valid == 0x13371337) {
        before->next = before->calc_succ();
        if (before->next != nullptr) {
          before->next->prev = before;
        }
      } else {
        this->min = after;
      }
      if (after != nullptr && after->valid == 0x13371337) {
        after->prev = after->calc_pred();
        if (after->prev != nullptr) {
          after->prev->next = after;
        }
      } else {
        this->max = before;
      }
    }
  }

  // baseline iterator creation
  Iterator begin() { return Iterator{min, nullptr}; }
  Iterator end() { return Iterator{nullptr, max}; }
  ConstIterator begin() const { return Iterator{min, nullptr}; }
  ConstIterator end() const { return Iterator{nullptr, max}; }
  ReverseIterator rbegin() { return Iterator{max, nullptr}; }
  ReverseIterator rend() { return Iterator{nullptr, min}; }

  // misc that can be implemented with the above or trivially
  void clear() {
    this->root = std::move(std::nullopt);
    this->_size = 0;
  }
  Mapped_T &at(const Key_T &key) {
    auto ret = this->find(key);
    if (ret == this->end()) {
      throw std::out_of_range{"key not in map"};
    }
    return (*ret).second;
  }
  const Mapped_T &at(const Key_T &key) const {
    auto ret = this->find(key);
    if (ret == this->end()) {
      throw std::out_of_range{"key not in map"};
    }
    return (*ret).second;
  }
  Mapped_T &operator[](const Key_T &key) {
    this->insert({key, {}});
    return this->at(key);
  }
  template <typename IT_T> void insert(IT_T range_beg, IT_T range_end) {
    while (range_beg != range_end) {
      auto [first, second] = *range_beg;
      this->insert(std::make_pair(first, second));
      ++range_beg;
    }
  }
  void erase(const Key_T &key) { this->erase(this->find(key)); }
  friend bool operator==(const Map &lhs, const Map &rhs) {
    if (lhs.size() != rhs.size()) {
      return false;
    }
    auto lhs_iter = lhs.begin();
    auto rhs_iter = rhs.begin();
    while (lhs_iter != lhs.end()) {
      if (*lhs_iter != *rhs_iter) {
        return false;
      }
      ++lhs_iter;
      ++rhs_iter;
    }
    return true;
  }
  friend bool operator!=(const Map &lhs, const Map &rhs) {
    return !(lhs == rhs);
  }
  friend bool operator<(const Map &lhs, const Map &rhs) {
    auto lhs_iter = lhs.begin();
    auto rhs_iter = rhs.begin();
    while (lhs_iter != lhs.end() && rhs_iter != rhs.end()) {
      if (*lhs_iter < *rhs_iter) {
        return true;
      }
      if (*lhs_iter != *rhs_iter) {
        return false;
      }
      ++lhs_iter;
      ++rhs_iter;
    }
    return lhs.size() < rhs.size();
  }
};
} // namespace cs440
#endif