二叉搜索树又称二叉排序树，它或者是一棵空树，或者是具有以下性质的二叉树:
1.若它的左子树不为空，则左子树上所有节点的值都小于根节点的值
2.若它的右子树不为空，则右子树上所有节点的值都大于根节点的值
3.它的左右子树也分别为二叉搜索树

#pragma once
#include<iostream>
using namespace std;template<class T>
struct bstnode
{T _val;bstnode* _left;bstnode* _right;bstnode(const T& val) :_val(val), _left(nullptr), _right(nullptr){}~bstnode(){_left = nullptr;_right = nullptr;_val = 0;}};template<class T>
class BST
{public:typedef bstnode<T> bstnode;BST() :_node(nullptr){}bool push(const T& data){bstnode* root = _node;bstnode* rootp = nullptr;if (_node == nullptr){bstnode *temp = new bstnode(data);_node = temp;return true;}while (root){if (data < root->_val){rootp = root;root = root->_left;}else if (data > root->_val){rootp = root;root = root->_right;}else{return false;}}bstnode *newnode = new bstnode(data);if (newnode->_val > rootp->_val){rootp->_right = newnode;}else{rootp->_left = newnode;}return true;}bool erase(const T&data){bstnode* root = _node;bstnode* rootp = nullptr;while (root){//找节点if (data < root->_val){rootp = root;root = root->_left;}else if (data > root->_val){rootp = root;root = root->_right;}elsebreak;}//如果为空直接返回falseif (root == nullptr)return false;if (root == _node)rootp = root;//如果root左边是空if (root->_left == nullptr){if (rootp->_left == root){if (root == _node){_node = root->_right;}else{rootp->_left = root->_right;}}else{if (root == _node){_node = root->_right;}else{rootp->_right = root->_right;}}delete  root;}//如果右边是空else if (rootp->_right == nullptr){if (rootp->_left == root){rootp->_left = root->_left;}else{rootp->_right = root->_left;}delete root;}//如果两边都不为空else{bstnode* find = root->_right;bstnode* findp = root;while (find->_left){findp = find;find = find->_left;}root->_val = find->_val;if (root == findp){findp->_right = find->_right;}else{findp->_left = find->_right;}delete find;}return true;}bool find(const T& data){bstnode* root = _node;while (root){if (root->_val < data){root = root->_left;}else if (root->_val > data){root = root->_right;}else{return true;}return false;}}void print(){print(_node);cout << endl;}private:void print(bstnode* root){if (root == nullptr){return;}print(root->_left);cout << root->_val << " ";print(root->_right);}bstnode* _node;
};