二叉搜索树的插入、搜索和删除

BinarySearchTree.h：

#ifndef BINARYSEARCHTREE_H_INCLUDED#define BINARYSEARCHTREE_H_INCLUDED#include<iostream>using namespace std;template <class T>class BinarySearchTree;template<class T>class TreeNode{private:    friend class BinarySearchTree<T>;    TreeNode* parent;                     //父结点    TreeNode* leftChild;                     //左孩子    TreeNode* rightChild;                     //右孩子    T data;                     //关键码public:    TreeNode(T data):data(data){        parent = leftChild = rightChild = NULL;    }    bool isLeaf(){        return (!leftChild && !rightChild);    }};template<class T>class BinarySearchTree{private:    TreeNode<T>* root;                       //根结点public:    BinarySearchTree(){        root = NULL;    }    ~BinarySearchTree(){        destory(root);    }    void destory(TreeNode<T>* node){                //销毁二叉树        TreeNode<T>* temp = node;        if(temp == NULL)            return;        destory(temp->leftChild);        destory(temp->rightChild);        delete temp;        temp = NULL;    }    TreeNode<T>* getRoot(){        return root;    }    void insert(T data){                       //插入新结点        TreeNode<T>* node = new TreeNode<T>(data);        if(!root){                        //如果树为空则设为根节点            root = node;        }else{            TreeNode<T>* pointer = root;            while(pointer){                if(pointer->data == data)         //如果已存在相同关键码，则返回                    return;                else if(pointer->data > data){       //如果要插入结点关键码比当前结点关键码小且左孩子指针为空，则设置为左孩子                    if(!pointer->leftChild){                        pointer->leftChild = node;                        node->parent = pointer;                        return;                    }else{               //否则当前指针向左移动                        pointer = pointer->leftChild;                    }                }else if(pointer->data < data){                    if(!pointer->rightChild){                        pointer->rightChild = node;                        node->parent = pointer;                        return;                    }else{                        pointer = pointer->rightChild;                    }                }            }        }    }    void print(TreeNode<T>* node){                    //打印二叉树，前序递归遍历         TreeNode<T>* pointer = node;         if (pointer != NULL) {            cout<<pointer->data<<" ";            print(pointer->leftChild);            print(pointer->rightChild);          }    }    TreeNode<T>* search(T data){                    //查找        TreeNode<T>* pointer = root;        while(pointer){            if(pointer->data > data)              //如果当前结点关键码大于要查找的关键码，继续查找其左子树                pointer = pointer->leftChild;            else if(pointer->data < data)            //如果当前结点关键码小于要查找的关键码，继续查找其右子树                pointer = pointer->rightChild;            else if(pointer->data == data){            //等于则返回当前结点                return pointer;            }        }        return NULL;                        //没找到返回NULL    }    void del(T data){        TreeNode<T>* pointer;        pointer = search(data);        if(pointer){            if(pointer->isLeaf()){               //要删除的结点为叶子结点时，直接删除此节点                if(pointer == root){                    root = NULL;                    return;                }                if(pointer->parent->leftChild == pointer)                    pointer->parent->leftChild = NULL;                else                    pointer->parent->rightChild = NULL;                delete pointer;                pointer = NULL;                return;            }else if(pointer->leftChild){            //如果不是叶子节点用复制删除法删除，默认选左子树中的最大值做替身，否则选右子树的最小值做替身                TreeNode<T>* node = pointer->leftChild;                while(node->rightChild)           //找到左子树的最大值                    node = node->rightChild;                if(node->leftChild){            //如果替身有左孩子，则用左孩子代替替身，否则将其父结点的右孩子指针置为空                    node->parent->rightChild = node->leftChild;                    node->leftChild->parent = node->parent;                }else{                    if(node->parent->rightChild == node)                        node->parent->rightChild = NULL;                    else                        node->parent->leftChild = NULL;                }                pointer->data = node->data;         //用替身的关键码代替要删除元素的关键码                delete node;                 //销毁替身                node = NULL;            }else{                TreeNode<T>* node = pointer->rightChild;                while(node->leftChild)                    node = node->leftChild;                if(node->rightChild){                    node->parent->leftChild = node->rightChild;                    node->rightChild->parent = node->parent;                }else{                    if(node->parent->leftChild == node)                        node->parent->leftChild = NULL;                    else                        node->parent->rightChild = NULL;                }                pointer->data = node->data;                delete node;                node = NULL;            }        }    }};#endif // BINARYSEARCHTREE_H_INCLUDE

主函数测试：main.cpp:

#include "BinarySearchTree.h"int main(){    BinarySearchTree<int> bin;    bin.insert(50);    bin.insert(60);    bin.insert(20);    bin.insert(10);    bin.insert(25);    bin.insert(23);    bin.insert(15);    bin.insert(16);    bin.print(bin.getRoot());    cout<<endl;    bin.del(50);    bin.print(bin.getRoot());    cout<<endl;    bin.del(20);    bin.print(bin.getRoot());    cout<<endl;    return 0;}