根节点应该有一个分配的节点，但保持为NULL.为什么不能为根分配节点? [英] Root node should have an assigned node, but remains NULL. Why can't I assign a node to my root?

问题描述

我正在以面向对象的格式编写一个二叉树.我以前有过使用二叉树的经验，但是自从接触到这已经有一段时间了.我的问题是我无法将节点分配给我的根.每次我在调试模式下检查时，其根始终为NULL.发生这种情况时，cur节点将包含它分配的所有信息.

I'm writing a binary tree in object-oriented format. I've had experience with binary trees before, but it's been a while since I've touched on this. My problem is that I'm unable to assign a node to my root. Every time I check in debugging mode, the root remains NULL. While this is happening, the cur node contains all the information it's assigned.

我尝试将我的根目录设为私有，并将this->root = NULL;更改为root-> = NULL;.我也尝试过将所有功能公开，但这并没有改变.我尝试将root的子级声明为NULL值，并将名称也声明为空字符串.

I've tried making my root private and changing this->root = NULL; to root-> = NULL;. I've also tried making all of my functions public, but it didn't make a difference. I tried declaring root's children to NULL values and name to an empty string as well.

main.cpp

#include <iostream>
#include <string>
#include <fstream>
#include "Friends.h"

using namespace std;

int main() {
    string line;
    ifstream file;
    file.open("friends.txt");

    Friends f;

    while (getline(file, line)) {
        f.insert(f.root, line);
    }
    f.print(f.root);

    system("pause");
    return 0;
}

Friends.cpp

#include "Friends.h"
#include <iostream>
#include <string>

using namespace std;

Friends::Friends() {
    this->root = NULL;
}

Friends::node* Friends::createNode(string& val) {
    node* newNode = new node();
    newNode->left = NULL;
    newNode->right = NULL;
    newNode->name = val;
    return newNode;
}

Friends::node* Friends::insert(node* cur, string& val) {
    if (!cur) {
        cur = createNode(val);
    }
    else if (val < cur->name) {
        insert(cur->left, val);
        return cur;
    }
    else if (val > cur->name) {
        insert(cur->right, val);
        return cur;
    }
    return NULL;
}

void Friends::print(node* cur) {
    if (!cur) {
        return;
    }
    print(cur->left);
    cout << cur->name << endl;
    print(cur->right);
}

Friends.h

#ifndef FRIENDS_H
#define FRIENDS_H

#include <string>

using namespace std;

class Friends {
private:
    struct node {
        string name;
        node* left;
        node* right;
    };
public:
    node* root;
    node* insert(node* cur, string&);
    void print(node* cur);
    Friends();
    node* createNode(string&);
};

#endif

根节点应该有一个节点，但是一直显示为NULL值.它也不会运行任何错误.它只是保留为NULL.

The root node should have a node, but has keeps showing up as a NULL value. It doesn't run with any errors either. It just remains as NULL.

推荐答案

更改自:

node* insert(node* cur, string&);

至:

node* insert(node* &cur, string&);

应该修复

当然，实现标头也应该更改

Of course the implementation header should also be changed

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