Problem in Binary Tree implementation

Question

Good evening, folks. I am trying to implement a binary tree with methods to insert(Insert,insertLeft and insertRight) and print (print).

All goes well until I try to insert a knot in the tree through the Insert method, i can create the no and assign a value to its value variable, but when trying to print the tree nothing appears, the root pointer always ends up pointing to NULL.

Thank you in advance

Follow the code:

class NodeTree {

public:

   int value;
   NodeTree * left;
   NodeTree * right;

   NodeTree() {
     value = 0;
   }

};

---

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

class BinaryTree {

public:

NodeTree * root;


BinaryTree() {
    root = NULL;
}



bool isEmpty() {
    return root == NULL;
}


void makeEmpty() {
    root = NULL;
}


void insert(int opcao,int num) {

    NodeTree * node = new NodeTree;
    node->value = num;

    if (opcao == 1) {
        insertRigth(node,root);
    }

    if (opcao == 2) {
        insertLeft(node,root);
    }

}

void insertRigth(NodeTree * node1,NodeTree * root1) {

    if (root1 == NULL) {
        node1->right = NULL;
        node1->left = NULL;
        root1 = node1;
    }
    else {
        insertRigth(node1,root1->right);
    }

}


void insertLeft(NodeTree * node1,NodeTree * root1) {

    if (root1 == NULL) {
        node1->right = NULL;
        node1->left = NULL;
        root1 = node1;
    }
    else {
        insertLeft(node1,root1->left);
    }

}

void print(NodeTree * obj) {

    if (obj == NULL) {
        cout << "A arvore esta vazia, nao e possivel imprimir\n";
        return;
    }

    print(obj->left);

    cout << obj->value << endl;

    print(obj->right);

  }

};

---

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

int main(){

BinaryTree arvore;
int sentinela = 0;
int opcao;
int numero;

while (sentinela != 3) {

    system("cls");
    cout << "Opcoes da Arvore Binaria:\n\n1-Inserir\n2-Exibir em Ordem\n3-Sair\n\nOpcao desejada:";
    cin >> sentinela;

    if (sentinela == 1) {
        system("cls");
        cout << "Deseja inserir o elemento em qual lado ? 1-Direita / 2-Esquerda: ";
        cin >> opcao;
        cout << "Digite um numero:";
        cin >> numero;
        arvore.insert(opcao, numero);
    }


    if (sentinela == 2) {
        system("cls");
        arvore.print(arvore.root);
        system("PAUSE");
    }

}

return 0;

}

Answer 1

i can create the no and assign a value to its value variable, but when trying to print the tree nothing appears, the root pointer always ends up pointing to NULL.

The problem is that this part of the function:

root1 = node1;

Doesn’t change where to root is pointing. To be able to do this, you can 1) pass the address of root:

void insertRigth(NodeTree *node1, NodeTree **root1)
{
    if (*root1 == NULL)
    {
        node1->right = NULL;
        node1->left = NULL;
        *root1 = node1;
    }
    else
    {
        insertRigth(node1, &(*root1)->right);
    }
}

Or 2) receive the root1 as a reference (because then you will be able to change the address of the original pointer), not needing to change the body of the old function, only the prototype of the function:

// Corpo continua igual.
void insertRigth(NodeTree *node1, NodeTree *&root1)