c++ - 二进制搜索树PostOrder和PreOrder遍历错误

我正在做此作业，我需要按顺序，后顺序和顺序打印二进制搜索树。但是，似乎只有我的顺序方法在起作用。我已使用以下测试用例来检查我的工作。

http://www.theteacher99.btinternet.co.uk/theteacher/newalevel/cp4_5_4.htm

您能否看一下下面的代码，看看我做错了什么。任何帮助/方向将不胜感激。您不必为我解决问题，只需让我知道我做错了什么。谢谢。

#include <iostream>
#include <fstream>
#include <cstddef>
#include <string>
#include <sstream>
#include <string>

using namespace std;

struct TreeNode
{
    string item;
    TreeNode *left;
    TreeNode *right;
};

class BinarySortTree
{
public:
    BinarySortTree();
    void readFile(string fileName);
    void insert(string key);
    void preorder();
    void postorder();
    void inorder();
    void test();

private:
    TreeNode *root;
    void insert(string key, TreeNode *node);
    void preorderTraverse(TreeNode *node);
    void postorderTraverse(TreeNode *node);
    void inorderTraverse(TreeNode *node);
};


//default constructor, create new binary tree
BinarySortTree::BinarySortTree()
{
    root = NULL;
}

//reads the file and puts items in the tree
void BinarySortTree::readFile(string fileName)
{
    ifstream inputStream(fileName.c_str());

    if(inputStream.is_open())
    {
        string line;

        while( getline(inputStream, line) )
        {
            insert(line);
        }
    }
}

void BinarySortTree::insert(string key)
{
    if(root != NULL)
    {
        insert(key, root);
    }
    else
    {
        root = new TreeNode;
        root->item = key;
        root->left = NULL;
        root->right = NULL;
    }
}

void BinarySortTree::insert(string key, TreeNode *node)
{
    bool done = false;

    while(!done)
    {
        if(key.compare(node->item) < 0)
        {
            if(node->left != NULL)
            {
                node = node->left;
            }
            else
            {
                node->left = new TreeNode;
                node->left->item = key;
                node->left->left = NULL;
                node->left->right = NULL;
                done = true;
            }
        }
        else if(key.compare(node->item) > 0)
        {
            if(node->right != NULL)
            {
                node = node->right;
            }
            else
            {
                node->right = new TreeNode;
                node->right->item = key;
                node->right->left = NULL;
                node->right->right = NULL;
                done = true;
            }
        }
        else if(key.compare(node->item) == 0)
        {
            done = true;
        }
    }
}

void BinarySortTree::preorder()
{
    cout << "PreOrder Traversal" << endl;
    preorderTraverse(root);
    cout << endl;

}

/*
   1. Start at the root node
   2. Traverse the left subtree
   3. Traverse the right subtree
*/
void BinarySortTree::preorderTraverse(TreeNode *node)
{
    if(node != NULL)
    {
        cout << node->item << " ";
        preorderTraverse(node->left);
        preorderTraverse(node->right);
    }

}

void BinarySortTree::postorder()
{
    cout << "PostOrder Traversal" << endl;
    postorderTraverse(root);
    cout << endl;
}

/*
   1. Traverse the left subtree
   2. Traverse the right subtree
   3. Visit the root node
*/
void BinarySortTree::postorderTraverse(TreeNode *node)
{
    if(node != NULL)
    {
        postorderTraverse(node->left);
        postorderTraverse(node->right);
        cout << node->item << " ";
    }
}

void BinarySortTree::inorder()
{
    cout << "InOrder Traversal" << endl;
    inorderTraverse(root);
    cout << endl;
}

/*
   1. Traverse the left subtree
   2. Visit the root node
   3. Traverse the right subtree
*/
void BinarySortTree::inorderTraverse(TreeNode *node)
{
    if(node!= NULL)
    {
        inorderTraverse(node->left);
        cout << node->item << " ";
        inorderTraverse(node->right);
    }
}

void BinarySortTree::test()
{
    cout << root->item << endl;
}


int main()
{
    string fileName = "a4.txt";
    BinarySortTree bst;
    bst.readFile(fileName);
    bst.test();

    bst.preorder();
    bst.postorder();
    bst.inorder();

    return 0;
}

最佳答案

你什么都没做错。我将其编译，并且工作正常，并通过了这些测试。我不必对您提供的代码进行任何更改-只需对其进行添加，即可正确地编译和初始化结构。

确保在left的构造函数中将right / NULL指针分配给TreeNode，并正确地将D节点作为root传入。还记得删除通过new TreeNode创建的所有节点。如果您在堆栈上创建它们(没有new的普通局部变量)，那么您当然不必删除它们。

关于c++ - 二进制搜索树PostOrder和PreOrder遍历错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/5287690/