Question

我现在正在使用二叉搜索树，但是我遇到了一些遍历方法的问题。它没有打印正确的数据。它甚至看起来像是从记忆中丢失了它。一切正常，直到添加第四个元素。你能看看吗？

标题文件：

    #ifndef TREENODE_H
    #define TREENODE_H
    #include<cstdlib>
    #include<iostream>

    template <class T>
    class Bintree
    {
        struct Node
        {
            T val;
            Node *left;
            Node *right;
        };
        public:
        Bintree();
        Bintree(const Bintree&);
        ~Bintree();
        Node* root;
        void preorder(Node*);
        void inorder(Node*);
        void postorder(Node*);
        Node* minimum(Node*);
        Node* findelement(Node*);
        Node* maximum(Node*);
        void add(T);
        void del(T);
        void delnode(Node*);
    };

    #endif

treenode.cpp文件

#include "treenode.h"

template<class T>
Bintree<T>::Bintree()
{
    root = nullptr;
}

template<class T>
Bintree<T>::Bintree(const Bintree<T>& source)
{
    root = copy(source.root, NULL);
}

template<class T>
Bintree<T>::~Bintree()
{
    delete root;
}

template<class T>
void Bintree<T>::preorder(Node* root)
{
    if(root==nullptr) return;
    std::cout<<root->val<<"\t";
    preorder(root->left);
    preorder(root->right);
}

template<class T>
void Bintree<T>::inorder(Node* root)
{
    if(root==nullptr) return;
    inorder(root->left);
    std::cout<<root->val<<"\t";
    inorder(root->right);
}

template<class T>
void Bintree<T>::postorder(Node* root)
{
    if(root==nullptr) return;
    postorder(root->left);
    postorder(root->right);
    std::cout<<root->val<<"\t";
}

template<class T>
typename Bintree<T>::Node* Bintree<T>::minimum(Node* root)
{
    if(!root->left) return root;
    else
    {
        while(root->left!=nullptr)
            root = root->left;
        return root;
    }
}

    template<class T>
    typename Bintree<T>::Node* Bintree<T>::maximum(Node* root)
    {
        if(!root->right) return root;
        else
        {
            while(root->right!=nullptr)
                root = root->right;
            return root;
        }
    }

    template<class T>
    void Bintree<T>::add(T x)
    {
        Node *p = new Node;
        p->left = nullptr;
        p->right = nullptr;
        p->val = x;
        if(root == nullptr)
            root = p;
        else
        {
            for(;;)
            {
                if(x<root->val)
                {
                    if(!root->left)
                    {
                        root->left = p;
                        break;
                    }
                    else root = root->left;
                }
                else
                {
                    if(!root->right)
                    {
                        root->right = p;
                        break;
                    }
                    else root = root->right;
                }
            }
        }
    }

main.cpp文件

#include "treenode.cpp" // When I write treenode.h it gives me
//an error like `Undefined reference to...` member functions. Why?

int main()
{
    try
    {
        Bintree<char> BST;
        BST.add('a');
        BST.add('c');
        BST.add('x');
        BST.add('y');
        std::cout<<"min: "<<BST.minimum(BST.root)->val;
        std::cout<<"max: "<<BST.maximum(BST.root)->val<<"\n";
        BST.preorder(BST.root);
    }
    catch (std::exception const &e)
    {
        std::cerr<<"Exception caught: "<<e.what()<<'\n';
    }
    return 0;
}

Answer 1

你的遍历没有任何问题。

您的add函数始终修改根。
它只应在插入空树时才这样做。

使用局部变量进行遍历：

template<class T>
void Bintree<T>::add(T x)
{
    Node *p = new Node;
    p->left = nullptr;
    p->right = nullptr;
    p->val = x;
    if(root == nullptr)
        root = p;
    else
    {
        Node* current = root;
        for(;;)
        {
            if(x<current->val)
            {
                if(!current->left)
                {
                    current->left = p;
                    break;
                }
                else current = current->left;
            }
            else
            {
                if(!current->right)
                {
                    current->right = p;
                    break;
                }
                else current = current->right;
            }
        }
    }
}

二叉搜索树 - 所有遍历方法都运行错误

1 个答案: