template<class K>
	struct BSTreeNode
	{
		BSTreeNode<K>* _left;
		BSTreeNode<K>* _right;
		K _key;
		BSTreeNode(const K& key)
			:_left(nullptr)
			, _right(nullptr)
			, _key(key)
		{}
	};
	template<class K>
	class BSTree
	{
		typedef BSTreeNode<K> Node;
	public:
		BSTree()
			:_root(nullptr)
		{}
		//insert
		bool insert(const K& key)
		{
			if (_root == nullptr)
			{
				//為空
				//直接就是給成根節(jié)點(diǎn)
				_root = new Node(key);
				return true;
			}
			Node* parent = nullptr;
			Node* cur = _root;
			//找到插入的位置
			while (cur)
			{
				if (cur->_key < key)
				{
					parent = cur;
					cur = cur->_right;
				}
				else if (cur->_key > key)
				{
					parent = cur;
					cur = cur->_left;
				}
				else
				{
					return false; //已經(jīng)有了，則不能插入
				}
			}
			cur = new Node(key);
			if (parent->_key > key)
			{
				//插入左邊
				parent->_left = cur;
			}
			else
			{
				//插入右邊
				parent->_right = cur;
			}
			return true;
		}
		bool Find(const K& key)
		{
			if (_root == nullptr)
			{
				return false;
			}
			Node* cur = _root;
			while (cur)
			{
				if (cur->_key > key)
				{
					cur = cur->_left;
				}
				else if (cur->_key < key)
				{
					cur = cur->_right;
				}
				else
				{
					return true;
				}
			}
			return false;
		}
		bool erase(const K& value)
		{
			if (_root == nullptr)
			{
				return false;
			}
			Node* parent = nullptr;
			Node* cur = _root;
			while (cur)
			{
				if (cur->_key > value)
				{
					parent = cur;
					cur = cur->_left;
				}
				else if (cur->_key < value)
				{
					parent = cur;
					cur = cur->_right;
				}
				else
				{
					//找到了，開(kāi)始刪除
					//情況一：要?jiǎng)h除的節(jié)點(diǎn)左孩子為空
					if (cur->_left == nullptr)
					{
						if (parent == nullptr)
						{
							//刪除的是根節(jié)點(diǎn)
							_root = cur->_right;
						}
						//判斷刪除的是左孩子節(jié)點(diǎn)還是右孩子節(jié)點(diǎn)以便更改連接關(guān)系
						if (parent->_left == cur)
						{
							parent->_left = cur->_right;
						}
						else
						{
							parent->_right = cur->_right;
						}
						delete cur;
					}
					else if (cur->_right == nullptr)
					{
						//情況二：要?jiǎng)h除的節(jié)點(diǎn)左孩子不為空、右孩子為空
						if (parent == nullptr)
						{
							//刪除的是根節(jié)點(diǎn)
							_root = cur->_left;
						}
						if (parent->_left == cur)
						{
							parent->_left = cur->_left;
						}
						else
						{
							parent->_right = cur->_left;
						}
						delete cur;
					}
					else
					{
						//情況三：要?jiǎng)h除的節(jié)點(diǎn)即有左孩子也有右孩子
						//使用替換法
						//兩種替換：1、用該節(jié)點(diǎn)的左子樹(shù)最大節(jié)點(diǎn) 2、用該節(jié)點(diǎn)右子樹(shù)的最小節(jié)點(diǎn)
						//這里使用第一種替換方法
						//找到用于替換的節(jié)點(diǎn)
						Node* maxParent = cur;
						Node* maxCur = cur->_right;
						while (maxCur->_right)
						{
							maxParent = maxCur;
							maxCur = maxCur->_right;
						}
						//
						cur->_key = maxCur->_key;
						//刪除用于替換的節(jié)點(diǎn)
						if (maxParent->_left == maxCur)
						{
							maxParent->_left = maxCur->_left;
						}
						else
						{
							maxParent->_right = maxCur->_left;
						}
						delete maxCur;
					}
					return true;
				}
			}
			//要?jiǎng)h除的節(jié)點(diǎn)不存在
			return false;
		}
		//由于類外使用不到私有成員_root
		//增加一個(gè)函數(shù)
		void inorder()
		{
			_inorder(_root);
		}
		//遞歸版
		Node* FindR(const K& key)
		{
			return _FindR(_root, key);
		}
		bool insertR(const K& key)
		{
			return _insertR(_root, key);
		}
		bool eraseR(const K& key)
		{
			return _eraseR(_root, key);
		}
	private:
		void _inorder(Node* root) //不需要在類外顯示調(diào)用它，所以放在私有
		{
			if (root == nullptr)
			{
				return;
			}
			_inorder(root->_left);
			cout << root->_key << " ";
			_inorder(root->_right);
		}
		Node* _FindR(Node* root, const K& key)
		{
			if (root == nullptr)
			{
				return nullptr;
			}
			if (root->_key > key)
			{
				_FindR(root->_left, key);
			}
			else if (root->_key < key)
			{
				_FindR(root->_right, key);
			}
			else
			{
				//找到了
				return root;
			}
		}
		bool _insertR(Node*& root, const K& key) //注意root加引用
		{
			if (root == nullptr)
			{
				root = new Node(key);
				return true;
			}
			if (root->_key > key)
			{
				_insertR(root->_left, key);
			}
			else if (root->_key < key)
			{
				_insertR(root->_right, key);
			}
			else
			{
				return false;
			}
		}
		bool _eraseR(Node*& root, const K& key)
		{
			if (root == nullptr)
			{
				//都已經(jīng)找到空了，表示不存在
				return false;
			}
			if (root->_key > key)
			{
				_eraseR(root->_left, key);
			}
			else if (root->_key < key)
			{
				_eraseR(root->_right, key);
			}
			else
			{
				//找到要?jiǎng)h除的節(jié)點(diǎn)了，開(kāi)始刪除
				Node* del = root;
				//左孩子為空
				if (root->_left == nullptr)
				{
					root = root->_right; //使用了引用，直接就是
				}
				else if (root->_right == nullptr)
				{
					//左孩子不為空，右孩子為空
					root = root->_left;
				}
				else
				{
					Node* min = root->_right;
					while (min->_left)
					{
						min = min->_left;
					}
					swap(min->_key, root->_key);
					// 遞歸到右子樹(shù)去刪除
					return _eraseR(root->_right, key);
				}
				delete del;
				return true;
			}
		}
	private:
		Node* _root;
	};

//二叉搜索樹(shù)key/value模型
namespace KV
{
	template<class K, class V>
	struct	BSTreeNode
	{
		BSTreeNode* _left;
		BSTreeNode* _right;
		K _key;
		V _value;
		BSTreeNode(const K& key, const V& value)
			:_left(nullptr)
			, _right(nullptr)
			, _key(key)
			, _value(value)
		{}
	};
	template<class K, class V>
	class BSTree
	{
		typedef BSTreeNode<K, V> Node;
	public:
		BSTree()
			:_root(nullptr)
		{}
		bool insert(const K& key, const V& value)
		{
			if (_root == nullptr)
			{
				_root = new Node(key, value);
				return true;
			}
			//找到要插入的位置
			Node* parent = nullptr;
			Node* cur = _root;
			while (cur)
			{
				if (cur->_key > key)
				{
					//在左子樹(shù)
					parent = cur;
					cur = cur->_left;
				}
				else if (cur->_key < key)
				{
					//在右子樹(shù)
					parent = cur;
					cur = cur->_right;
				}
				else
				{
					return false;
				}
			}
			cur = new Node(key, value);
			//
			if (parent->_key > key)
			{
				//插入左孩子節(jié)點(diǎn)
				parent->_left = cur;
			}
			else
			{
				parent->_right = cur;
			}
			return true;
		}
		Node* Find(const K& key)
		{
			if (_root == nullptr)
			{
				return nullptr;
			}
			Node* cur = _root;
			while (cur)
			{
				if (cur->_key > key)
				{
					//在左子樹(shù)
					cur = cur->_left;
				}
				else if (cur->_key < key)
				{
					//在右子樹(shù)
					cur = cur->_right;
				}
				else
				{
					//相等，找到了
					return cur;
				}
			}
			//不存在
			return nullptr;
		}
		bool Erase(const K& key)
		{
			if (_root == nullptr)
			{
				return false;
			}
			//找到要?jiǎng)h除的節(jié)點(diǎn)
			Node* parent = nullptr;
			Node* cur = _root;
			while (cur)
			{
				if (cur->_key > key)
				{
					parent = cur;
					cur = cur->_left;
				}
				else if (cur->_key < key)
				{
					parent = cur;
					cur = cur->_right;
				}
				else
				{
					//找到了
					//開(kāi)始刪除
					//情況一：要?jiǎng)h除的節(jié)點(diǎn)沒(méi)有左子樹(shù)
					if (cur->_left == nullptr)
					{
						if (parent == nullptr)
						{
							//刪除的是根節(jié)點(diǎn)
							_root = cur->_right;
						}
						//判斷刪除的是左孩子節(jié)點(diǎn)還是右孩子節(jié)點(diǎn)，方便更改連接關(guān)系
						if (parent->_left = cur)
						{
							parent->_left = cur->_right;
						}
						else
						{
							parent->_right = cur->_right;
						}
						delete cur;
					}
					else if (cur->_right == nullptr)
					{
						//情況二：要?jiǎng)h除的節(jié)點(diǎn)左孩子不為空，，右孩子為空
						if (parent == nullptr)
						{
							_root = cur->_left;
						}
						if (parent->_left = cur)
						{
							parent->_left = cur->_left;
						}
						else
						{
							parent->_right = cur->_left;
						}
						delete cur;
					}
					else
					{
						//情況三：要?jiǎng)h除的節(jié)點(diǎn)既有左孩子也有右孩子
						//要使用替換法刪除
						//使用右子樹(shù)的最小節(jié)點(diǎn)進(jìn)行替換
						Node* minParent = cur;
						Node* minCur = cur->_right;
						//找到右子樹(shù)的最小節(jié)點(diǎn)
						while (minCur->_left)
						{
							minParent = minCur;
							minCur = minCur->_left;
						}
						//替換
						cur->_key = minCur->_key;
						cur->_value = minCur->_value;
						//刪除替換節(jié)點(diǎn)，并更改連接關(guān)系
						if (minParent->_left == minCur)
						{
							minParent->_left = minCur->_right;
						}
						else
						{
							minParent->_right = minCur->_right;
						}
						delete minCur;
					}
					return true;
				}
			}
			return false;
		}
		void inorder()
		{
			_inorder(_root);
		}
	private:
		void _inorder(Node* root)
		{
			if (root == nullptr)
			{
				return;
			}
			_inorder(root->_left);
			cout << root->_key << ":" << root->_value << endl;
			_inorder(root->_right);
		}
	private:
		Node* _root;
	};
}