表示二叉树的节点类C ++

Question

I have created a node.h class, defining a class called node for representing a binary tree(any type). It seems to be that the constructor isn't working. The errors are below.Ive only started writing constructors within classes like these, and this is the first ive encountered binary trees. Can anyone point me in the right direction on how to fix these errors and make my code work? Thanks.

Node.h

#ifndef NODE_H
#define NODE_H
#include <iostream>

//an object of type node holds 3 things
// - an item (oftype t)
// - a left subtree
// - a right subtree

template<typename T>
class Node {
public:
    Node(T item); //constructor to create a leaf node
    Node(T item, Node *lft, Node *rht); //constructor which creates an internal node 
    ~Node(); //Destructor

    //public data member functions:
    bool searchTree(T key);
    void printTree();

private:
    //private data member functions:
    //..
};

//constructor 
template<typename T>
Node<T>::Node(T i, Node<T> *l, Node<T> *r) {
    item = i;
    lft = NULL;
    rht = NULL;
}

//constructor //is this correct?
template <typename T>
Node<T>::Node(T i) { //should i be a parameter here?
    item = i; //is this right?
}

//destructor
template <typename T>
Node<T>::~Node() {
    delete left;
    delete right;
    //delete;
}


//print tree method
template <typename T>
void Node<T>::printTree() {
    if (lft != NULL) {
        lft->printTree();
        cout << item << endl;//alphabetical order
    }

    if (rht != NULL) {
        rht->printTree();
        //cout << item << endl; //post order
    }
}

//search Tree method
template <typename T>
bool Node<T>::searchTree(T key) {
    bool found = false;
    if (item == key) {
        return true;
    }
    if (left != NULL) {
        found = left->searchTree(key);
        if (found) return true;
    }
    if (right != NULL) {
        return right->searchTree(key);
    }
    return false; //if left and right are both null & key is not the search item, then not found == not in the tree.
}

#endif

Main.cpp

#include "Node.h"
#include <iostream>
using namespace std;

//set up tree method
Node<string> *setUpTree() {
    Node<string> *s_tree =
        new Node<string>("Sunday",
        new Node<string>("monday",
        new Node<string>("Friday"),
        new Node<string>("Saturday")),
        new Node<string>("Tuesday",
        new Node<string>("Thursday"),
        new Node<string>("Wednesday")));
}

int main() {

    Node<string> *s_tree;
    s_tree = setUpTree();

    cout << "Part 2 :Priting tree vals " << endl << endl;
    s_tree->printTree();
    cout << endl;

    //search for range of tree values
    //searchTree(s_tree, "Sunday");
    //searchTree(s_tree, "Monday");

    return 0;
}

Answer 1

There is no declarations of members you use in your constructor and other methods. The compiler does not know what rht or right means. Judging from your code the class should look more like this:

template<typename T>
class Node {
public:
    Node(T item); //constructor to create a leaf node
    Node(T item, Node *lft, Node *rht); //constructor which creates an internal node 
    ~Node(); //Destructor

    //public data member functions:
    bool searchTree(T key);
    void printTree();

private:
    Node* left;
    Node* right;
    T item;
    //private data member functions:
    //..
};

So now the compiler knows what left , right and item mean. Now you can use these identifiers inside member functions of that class. Note that compiler still does not know what rht or lft are, so you should replace them with right and left .

Hope this helps