如何正确使用模板类的嵌套类？

时间：2015-02-13 09:50:21

标签： c++ nested template-classes

一切！ 我正在尝试实现一个简单的模板类二进制搜索树。 我遇到了函数定义的几个问题。 以下是我的BST类代码

#ifndef BINARY_SEARCH_TREE_H
#define BINARY_SEARCH_TREE_H

#include <iostream>
#include <stdlib.h>

using namespace std;

template<class T>
class BST
{
    struct TreeNode {
        TreeNode* left;
        TreeNode* right;
        T value;
    };

    //member functions
    void destroyTree(TreeNode* leaf);
    void insert(T key, TreeNode* leaf);
    TreeNode* search(T key, TreeNode* leaf);
    void printInOrder(TreeNode* leaf);
    void printPreOrder(TreeNode* leaf);
    void printPostOrder(TreeNode* leaf);

    //memebr variables
    TreeNode* root;
public:

    enum Traversal { INORDER, PREORDER, POSTORDER };

    BST();
    BST(T key);
    ~BST();

    void insert(T key);
    TreeNode* search(T key);
    void printTree(T option);
    void destroyTree();
};

template <class T>
BST<T>::BST()
{
    root = NULL;
};

template <class T>
BST<T>::BST(T key)
{
    root = new TreeNode;
    root->left = NULL;
    root->right = NULL;
    root->value = key;
};

template <class T>
BST<T>::~BST()
{
    destroyTree();
};

template <class T>
void BST<T>::destroyTree(TreeNode* leaf)
{
    if (leaf->left != NULL) destroyTree(leaf->left);
    if (leaf->right != NULL) destroyTree(leaf->right);
    delete leaf;
    leaf = nullptr;
};

template <class T>
void insert(T key, BST<T>::TreeNode* leaf)
{
    if (leaf->value == key)
    {
        cout << "failed inserting node: duplicate item" << endl;
        return;
    }
    else if (leaf->value < key)
    {
        if (leaf->right != NULL) insert(key, leaf->right);
        else
        {
            TreeNode newNode = new TreeNode;
            newNode->left = NULL;
            newNode->right = NULL;
            newNode->value = key;
            leaf->right = newNode;
        }
    }
    else
    {
        if (leaf->left != NULL) insert(key, leaf->left);
        else
        {
            TreeNode newNode = new TreeNode;
            newNode->left = NULL;
            newNode->right = NULL;
            newNode->value = key;
            leaf->left = newNode;
        }
    }
};

template <class T>
BST<T>::TreeNode* BST<T>::search(T key, TreeNode* leaf)
{
    if (leaf == NULL) return NULL;
    if (leaf->value == key) return leaf;
    else if (leaf->vluae < key) return search(key, leaf->right);
    else return search(key, leaf->left);
};

template <class T>
void printInOrder(TreeNode* leaf)
{
    if (leaf->left != NULL) printInOrder(leaf->left);
    cout << leaf->value << " ";
    if (leaf->right != NULL) printInOrder(leaf->right);
};

template <class T>
void printPreOrder(TreeNode* leaf)
{
    cout << leaf->value << " ";
    if (leaf->left != NULL) printPreOrder(leaf->left);
    if (leaf->right != NULL) printPreOrder(leaf->right);
};

template <class T>
void printPostOrder(TreeNode* leaf)
{
    if (leaf->left != NULL) printPostOrder(leaf->left);
    if (leaf->right != NULL) printPostOrder(leaf->right);
    cout << leaf->value << " ";
};

template <class T>
void BST<T>::insert(int key)
{
    if (this->root == NULL)
    {
        this->root = new TreeNode;
        this->root->left = NULL;
        this->root->right = NULL;
        this->root->value = key;
    }
    else insert(key, root);
};

template <class T>
BST<T>::TreeNode* BST<T>::search(int key)
{
    search(key, this->root);
};

template <class T>
void BST<T>::printTree(int option)
{
    switch (option)
    {
    case BST<T>::INORDER:
        printInOrder(this->root);
        cout << endl;
        break;
    case BST<T>::POSTORDER:
        printPostOrder(this->root);
        cout << endl;
        break;
    case BST<T>::PREORDER:
        printPreOrder(this->root);
        cout << endl;
        break;
    }
};

template <class T>
void BST<T>::destroyTree()
{
    destroyTree(this->root);
};

#endif

正如您所看到的，对于void insert(T key, BST<T>::TreeNode* leaf)和BST<T>::TreeNode* BST<T>::search(T key, TreeNode* leaf)函数，我需要使用TreeNode类来执行操作，例如返回它的对象或将其传递给函数，这是一个类BST中定义的嵌套类型。 我得到的错误是语法错误，但我不知道我在代码中做错了什么。 任何建议或意见将不胜感激！

2 个答案:

答案 0 :(得分：2)

你应该：

  • 将每个TreeNode替换为BST<T>::TreeNode，因为可能存在不同的TreeNode定义，因此编译器需要知道您正在谈论的那个。

    < / LI>

  • 在每个typename前添加BST<T>::TreeNode。 BST<T>::TreeNode可能有几个不同的定义，甚至一些不是类型的定义，所以你需要告诉编译器它是一个类型。

答案 1 :(得分：1)

#include <iostream>
#include <stdlib.h>

using namespace std;

template<class T>
class BST
{
    struct TreeNode {
        TreeNode* left;
        TreeNode* right;
        T value;
    };

    //member functions
    void destroyTree(TreeNode* leaf);
    void insert(T key, TreeNode* leaf);
    TreeNode* search(T key, TreeNode* leaf);
    void printInOrder(TreeNode* leaf);
    void printPreOrder(TreeNode* leaf);
    void printPostOrder(TreeNode* leaf);

    //memebr variables
    TreeNode* root;
public:

    enum Traversal { INORDER, PREORDER, POSTORDER };
    BST();
    BST(T key);
    ~BST();

    void insert(T key);
    TreeNode* search(T key);
    void printTree(T option);
    void destroyTree();
};

template <class T>
BST<T>::BST()
{
    root = NULL;
};

template <class T>
BST<T>::BST(T key)
{
    root = new TreeNode;
    root->left = NULL;
    root->right = NULL;
    root->value = key;
};

template <class T>
BST<T>::~BST()
{
    destroyTree();
};

template <class T>
void BST<T>::destroyTree(TreeNode* leaf)
{
    if (leaf->left != NULL) destroyTree(leaf->left);
    if (leaf->right != NULL) destroyTree(leaf->right);
    delete leaf;
    leaf = nullptr;
};

template <class T>
void BST<T>::insert(T key, typename BST<T>::TreeNode* leaf)
{
    if (leaf->value == key)
    {
        cout << "failed inserting node: duplicate item" << endl;
        return;
    }
    else if (leaf->value < key)
    {
        if (leaf->right != NULL) insert(key, leaf->right);
        else
        {
            BST<T>::TreeNode* newNode = new TreeNode;
            newNode->left = NULL;
            newNode->right = NULL;
            newNode->value = key;
            leaf->right = newNode;
        }
    }
    else
    {
        if (leaf->left != NULL) insert(key, leaf->left);
        else
        {
            BST<T>::TreeNode* newNode = new TreeNode;
            newNode->left = NULL;
            newNode->right = NULL;
            newNode->value = key;
            leaf->left = newNode;
        }
    }
};

template <class T>
typename BST<T>::TreeNode* BST<T>::search(T key, typename BST<T>::TreeNode* leaf)
{
    if (leaf == NULL) return NULL;
    if (leaf->value == key) return leaf;
    else if (leaf->vluae < key) return search(key, leaf->right);
    else return search(key, leaf->left);
};

template <class T>
void printInOrder(typename BST<T>::TreeNode* leaf)
{
    if (leaf->left != NULL) printInOrder(leaf->left);
    cout << leaf->value << " ";
    if (leaf->right != NULL) printInOrder(leaf->right);
};

template <class T>
void printPreOrder(typename BST<T>::TreeNode* leaf)
{
    cout << leaf->value << " ";
    if (leaf->left != NULL) printPreOrder(leaf->left);
    if (leaf->right != NULL) printPreOrder(leaf->right);
};

template <class T>
void printPostOrder(typename BST<T>::TreeNode* leaf)
{
    if (leaf->left != NULL) printPostOrder(leaf->left);
    if (leaf->right != NULL) printPostOrder(leaf->right);
    cout << leaf->value << " ";
};

template <class T>
void BST<T>::insert(T key)
{
    if (this->root == NULL)
    {
        this->root = new TreeNode;
        this->root->left = NULL;
        this->root->right = NULL;
        this->root->value = key;
    }
    else insert(key, root);
};

template <class T>
typename BST<T>::TreeNode* BST<T>::search(T key)
{
    search(key, this->root);
};

template <class T>
void BST<T>::printTree(T option)
{
    switch (option)
    {
        case BST<T>::INORDER:
            printInOrder(this->root);
            cout << endl;
            break;
        case BST<T>::POSTORDER:
            printPostOrder(this->root);
            cout << endl;
            break;
        case BST<T>::PREORDER:
            printPreOrder(this->root);
            cout << endl;
            break;
    }
};

template <class T>
void BST<T>::destroyTree()
{
    destroyTree(this->root);
};

现在应该工作，但充满了小错误，如： TreeNode newNode = new TreeNode;， template <class T> void insert代替template <class T> void BST<T>::insert

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