C++ 用红黑树模拟实现set、map的示例代码

template<class T>
struct RBTreeNode
{
	RBTreeNode<T>* _left;
	RBTreeNode<T>* _right;
	RBTreeNode<T>* _parent;
	T _data;
	Colour _col;
	RBTreeNode(const T& data)
		:_left(nullptr)
		,_right(nullptr)
		,_parent(nullptr)
		,_data(data)
		,_col(RED)
	{}
};

//返回的迭代器指向的数据可修改
iterator begin()
{
	Node* subLeft = _root;
	while (subLeft->_left)
	{
		subLeft = subLeft->_left;
	}
	return iterator(subLeft);
}
//返回的迭代器指向的数据不可修改
const_iterator begin() const
{
	Node* subLeft = _root;
	while (subLeft->_left)
	{
		subLeft = subLeft->_left;
	}
	return const_iterator(subLeft);
}

iterator end()
{
	return iterator(nullptr);
}
const_iterator end() const
{
	return const_iterator(nullptr);
}

iterator Find(const K& key)
{
	KeyOfT kot;
	Node* cur = _root;
	while (cur)
	{
		if (kot(cur->_data) < key)
		{
			cur = cur->_right;
		}
		else if (kot(cur->_data) > key)
		{
			cur = cur->_left;
		}
		else
		{
			return iterator(cur);
		}
	}
	return end();
}

pair<iterator, bool> Insert(const T& data)
{
	//为空
	if (_root == nullptr)
	{
		_root = new Node(data);
		_root->_col = BLACK;//根节点都是黑色的，特殊处理
		return make_pair(iterator(_root), true);
	}
	//非空
	KeyOfT kot;
	Node* cur = _root;
	Node* parent = nullptr;
	while (cur)
	{
		if (kot(cur->_data) < kot(data))
		{
			parent = cur;
			cur = cur->_right;
		}
		else if (kot(cur->_data) > kot(data))
		{
			parent = cur;
			cur = cur->_left;
		}
		else
		{
			return make_pair(iterator(cur), false);
		}
	}
	//插入新节点
	cur = new Node(data);//红色的
	if (kot(parent->_data) < kot(data))
	{
		parent->_right = cur;
	}
	else
	{
		parent->_left = cur;
	}
	cur->_parent = parent;
	Node* newnode = cur;

	//调整颜色
	while (parent && parent->_col == RED)
	{
		Node* grandfather = parent->_parent;//爷爷节点
		//父节点在爷爷节点的左边，那么叔叔节点在右边
		if (parent == grandfather->_left)
		{
			Node* uncle = grandfather->_right;
			//情况一：叔叔存在且为红
			if (uncle && uncle->_col == RED)
			{
				grandfather->_col = RED;
				uncle->_col = parent->_col = BLACK;
				cur = grandfather;//爷爷不是根，向上更新
				parent = cur->_parent;
			}
			//情况二：叔叔不存在/存在且为黑
			else
			{
				//单旋
				if (cur == parent->_left)
				{
					RotateR(grandfather);//右单旋
					parent->_col = BLACK;//变色
					grandfather->_col = RED;
				}
				//左右双旋 
				// cur == parent->_right
				else
				{
					RotateL(parent);//先左单旋
					RotateR(grandfather);//再右单旋
					grandfather->_col = RED;//变色
					cur->_col = BLACK;
				}
			}
		}
		else//父节点在右边，叔叔在左边
		{
			Node* uncle = grandfather->_left;
			//情况一：叔叔存在且为红
			if (uncle && uncle->_col == RED)
			{
				grandfather->_col = RED;
				uncle->_col = parent->_col = BLACK;
				cur = grandfather;//爷爷不是根，向上更新
				parent = cur->_parent;
			}
			//情况二：叔叔不存在/存在且为黑
			else
			{
				//单旋
				if (cur == parent->_right)
				{
					RotateL(grandfather);//左单旋
					parent->_col = BLACK;//变色
					grandfather->_col = RED;
				}
				//右左双旋 
				// cur == parent->_left
				else
				{
					RotateR(parent);//先右单旋
					RotateL(grandfather);//再左单旋
					grandfather->_col = RED;//变色
					cur->_col = BLACK;
				}
				break;//经过情况二后跳出
			}
		}
	}
	_root->_col = BLACK;//统一处理，根必须是黑的
	return make_pair(iterator(newnode), true);
}

//左单旋
void RotateL(Node* parent)
{
	Node* subR = parent->_right;
	Node* subRL = subR->_left;
	parent->_right = subRL;
	//不为空
	if (subRL)
	{
		subRL->_parent = parent;
	}
	subR->_left = parent;
	Node* ppnode = parent->_parent;
	parent->_parent = subR;
	//处理parent如果为根
	if (parent == _root)
	{
		_root = subR;
		subR->_parent = nullptr;
	}
	//不为根，处理与ppnode的连接
	else
	{
		if (ppnode->_left == parent)
		{
			ppnode->_left = subR;
		}
		else
		{
			ppnode->_right = subR;
		}
		subR->_parent = ppnode;
	}
}

//右单旋
void RotateR(Node* parent)
{
	Node* subL = parent->_left;
	Node* subLR = subL->_right;
	parent->_left = subLR;
	//不为空
	if (subLR)
	{
		subLR->_parent = parent;
	}
	subL->_right = parent;
	Node* ppnode = parent->_parent;
	parent->_parent = subL;

	if (parent == _root)
	{
		_root = subL;
		subL->_parent = nullptr;
	}
	else
	{
		if (ppnode->_left == parent)
		{
			ppnode->_left = subL;
		}
		else
		{
			ppnode->_right = subL;
		}
		subL->_parent = ppnode;
	}
}

template<class T, class Ref, class Ptr>
struct RBTreeIterator
{
	typedef RBTreeNode<T> Node;
	typedef RBTreeIterator<T, Ref, Ptr> Self;

	Node* _node;
	RBTreeIterator(Node* node)
		:_node(node)
	{}

	Ref operator*()
	{
		return _node->_data;
	}
	Ptr operator->()
	{
		return &_node->_data;
	}
	//前置++
	Self& operator++()
	{
		//右子树存在
		if (_node->_right)
		{
			//下一个节点在右子树的最左边
			Node* subLeft = _node->_right;
			while (subLeft->_left)
			{
				subLeft = subLeft->_left;
			}
			_node = subLeft;
		}
		//右子树不存在
		else
		{
			Node* cur = _node;
			Node* parent = cur->_parent;
			//cur是parent的左子树，parent就是下一个
			while (parent && parent->_right == cur)
			{
				cur = parent;
				parent = parent->_parent;
			}
			_node = parent;
		}
		return *this;
	}
	//前置--
	Self& operator--()//与前置++的逻辑相反
	{
		//左子树存在
		if (_node->_left)
		{
			//下一个节点是左子树的最右一个
			Node* subRight = _node->_left;
			while (subRight->_right)
			{
				subRight = subRight->_right;
			}
			_node = subRight;
		}
		//左子树不存在
		else
		{
			Node* cur = _node;
			Node* parent = cur->_parent;
			//cur是parent的右子树时parent就是下一个
			while (parent && parent->_left == cur)
			{
				cur = parent;
				parent = parent->_parent;
			}
			_node = parent;
		}
		return *this;
	}

	bool operator!=(const Self& s)
	{  
		return _node != s._node;
	}
	bool operator==(const Self& s)
	{
		return _node == s._node;
	}
};

template<class K>
class set
{
	//仿函数
	struct SetKeyOfT
	{
		const K& operator()(const K& key)
		{
			return key;
		}
	};
public:
	typedef typename RBTree<K, const K, SetKeyOfT>::iterator iterator;
	typedef typename RBTree<K, const K, SetKeyOfT>::const_iterator const_iterator;
	//迭代器
	iterator begin()
	{
		return _t.begin();
	}
	const_iterator begin() const
	{
		return _t.begin();
	}
	iterator end()
	{
		return _t.end();
	}
	const_iterator end() const
	{
		return _t.end();
	}
	//插入
	pair<iterator, bool> Insert(const K& key)
	{
		return _t.Insert(key);
	}
	//查找
	iterator Find(const K& key)
	{
		_t.Find(key);
	}
private:
	RBTree<K, const K, SetKeyOfT> _t;
};

template<class K, class V>
class map
{
	struct MapKeyOfT
	{
		const K& operator()(const pair<K, V>& kv)
		{
			return kv.first;
		}
	};

public:
	typedef typename RBTree<K, pair<const K, V>, MapKeyOfT>::iterator iterator;
	typedef typename RBTree<K, pair<const K, V>, MapKeyOfT>::const_iterator const_iterator;
	//迭代器
	iterator begin()
	{
		return _t.begin();
	}
	const_iterator begin() const
	{
		return _t.begin();
	}
	iterator end()
	{
		return _t.end();
	}
	const_iterator end() const
	{
		return _t.end();
	}

	//插入
	pair<iterator, bool> Insert(const pair<K, V>& kv)
	{
		return _t.Insert(kv);
	}

	//查找
	iterator Find(const K& key)
	{
		_t.Find(key);
	}

	//operator[]
	V& operator[](const K& key)
	{
		pair<iterator, bool> ret = Insert(make_pair(key, V()));
		return ret.first->second;
	}
private:
	RBTree<K, pair<const K, V>, MapKeyOfT> _t;
};