【数据结构】什么是二叉搜索(排序)树?

int a[] = { 8, 3, 1, 10, 6, 4, 7, 14, 13 };

namespace key_value
{
	template<class K,class V>
	struct BSTreeNode
	{
		BSTreeNode<K,V>* _left;
		BSTreeNode<K,V>* _right;
		K _key;
		V _value;
		BSTreeNode(const K& key = K(), const V& value = V())
			:_left(nullptr)
			, _right(nullptr)
			, _key(key)
			, _value(value)
		{}
	};

	template<class K, class V>
	class BSTree
	{
		typedef BSTreeNode<K,V> Node;
	public:
		BSTree()
			:_root(nullptr)
		{}

		BSTree(const BSTree<K,V>& t)
		{
			_root = Copy(t._root);
		}

		BSTree<K,V>& operator=(BSTree<K,V> t)
		{
			swap(_root, t._root);
			return *this;
		}

		~BSTree()
		{
			Destroy(_root);
		}

		void InOrder()
		{
			_InOrder(_root);
			cout << endl;
		}

		Node* FindR(const K& key)
		{
			return _FindR(_root, key);
		}

		bool InsertR(const K& key, const V& value)
		{
			return _InsertR(_root, key, value);
		}

		bool EraseR(const K& key)
		{
			return _EraseR(_root, key);
		}

	private:
		Node* Copy(Node* root)
		{
			if (root == nullptr)
				return nullptr;
			Node* copynode = new Node(root->_key);
			copynode->_left = Copy(root->_left);
			copynode->_right = Copy(root->_right);
			return copynode;
		}

		void Destroy(Node*& root)
		{
			if (root == nullptr)
				return;
			Destroy(root->_left);
			Destroy(root->_right);
			delete root;
			root == nullptr;
		}

		bool _EraseR(Node*& root, const K& key)
		{
			if (root == nullptr)
			{
				return false;
			}
			if (root->_key < key)
			{
				_EraseR(root->_right, key);
			}
			else if (root->_key > key)
			{
				_EraseR(root->_left, key);
			}
			else
			{
				Node* del = root;
				if (root->_left == nullptr)
				{
					root = root->_right;
				}
				else if (root->_right == nullptr)
				{
					root = root->_left;
				}
				else
				{
					Node* leftMax = root->_left;
					while (leftMax->_right)
					{
						leftMax = leftMax->_right;
					}
					swap(root->_key, leftMax->_key);
					return _EraseR(root->_left, key);
				}
				delete del;
				return true;
			}
		}

		bool _InsertR(Node*& root, const K& key, const V& value)
		{
			if (root == nullptr)
			{
				root = new Node(key,value);
				return true;
			}
			if (root->_key < key)
			{
				_InsertR(root->_right, key, value);
			}
			else if (root->_key > key)
			{
				_InsertR(root->_left, key, value);
			}
			else
			{
				return false;
			}
		}

		Node* _FindR(Node* root, const K& key)
		{
			if (root == nullptr)
			{
				return nullptr;
			}
			if (root->_key < key)
			{
				_FindR(root->_right, key);
			}
			else if (root->_key > key)
			{
				_FindR(root->_left, key);
			}
			else
			{
				return root;
			}
		}

		void _InOrder(Node* root)
		{
			if (root == nullptr)
				return;
			_InOrder(root->_left);
			cout << root->_key << ":" << root->_value << endl;
			_InOrder(root->_right);
		}

		Node* _root;
	};

	void TestBSTree1()//小字典
	{
		BSTree<string, string> dict;
		dict.InsertR("insert", "插入");
		dict.InsertR("sort", "排序");
		dict.InsertR("right", "右边");
		dict.InsertR("date", "日期");

		string str;
		while (cin >> str)	//按Ctrl+Z终止输入
		{
			BSTreeNode<string, string>* ret = dict.FindR(str);
			if (ret)
			{
				cout << ret->_value << endl;
			}
			else
			{
				cout << "无该单词" << endl;
			}
		}
	}

	void TestBSTree2()//统计水果出现次数
	{
		string arr[] = { "苹果", "西瓜", "苹果", "西瓜", "苹果", "苹果", "西瓜","苹果", "香蕉", "苹果", "香蕉" };
		BSTree<string, int> countTree;
		for (const auto& str : arr)
		{
			// 先查找水果在不在搜索树中
			// 1、不在，说明水果第一次出现，则插入<水果, 1>
			// 2、在，则查找到的节点中水果对应的次数++
			BSTreeNode<string, int>* ret = countTree.FindR(str);
			if (ret == NULL)
			{
				countTree.InsertR(str, 1);
			}
			else
			{
				ret->_value++;
			}
		}
		countTree.InOrder();
	}
}