Need help fixing a segmentation fault (core dumped)

Question

friends. So I'm creating a Binary Search Tree Class in ubuntu using vim as my editor, and when I run my program I always get a segmentation fault(core dumped) error. The weird thing is that when I run this program on NetBeans, it worked perfectly. this is my code

#include <iostream>
using namespace std;


class BST
{

struct node {
    int data;
    node* left;
    node* right;

};


private:
node* root;


node* addHelper(node* temp, int data)
{
    if(temp == NULL)
    {
       temp = new node;
       temp->left = temp->right = NULL;
       temp->data = data;
       return temp;
    }
    if(data < temp->data)
    {
    temp->left = addHelper(temp->left, data);
    }
    else if(data > temp->data)
    {
    temp->right = addHelper(temp->right, data);
    }
    return temp;
}

void printHelper(node* cur)
{
   if(cur == NULL)
   {
       return;
   }
   else {
        printHelper(cur->left);
        cout << cur->data << " ";
        printHelper(cur->right);
   }
}



public:

void add(int value)
{
   root = addHelper(root, value);
}



void printInorder()
{
    printHelper(root);
}


};

int main()
{
   cout << "Second Test, linux runnning sucsesfully"<<endl;
   BST mytree;
   mytree.add(20);
   mytree.add(25);
   mytree.add(10);
   mytree.add(22);
   mytree.add(15);
   mytree.add(12);
   mytree.add(23);

  mytree.printInorder();
  return 0;
}

I already use gdb to debug, and it pointed me an error on the printHelper function but I can't see the error. if you know how to fix this please help me. thank you in advance

Answer 1

Certianly yes the problem is the data member root is used and not initialized

Solution for the problem

public:
BST(){
  root = new node();
}

If at all the use case demands some more operations in the constructor you can also use the initializer list which is good in terms of readability. Just an add-on you should always initialize const and reference using the initializer list.

Or using the initializer list

public:
BST(node* root):root(root){
    //Any other initialization /Operation
}

Or give it a NULL (or nullptr, in the most recent C++ standard).

public:
BST() : root(NULL) { }

Our default ctor here makes it NULL (replace with nullptr if needed), the second constructor will initialize it with the value passed..

Answer 2

The fix is just initialize the root as NULL . [Do not allocate anything there.] constructor must be like below

BST() {
  root = NULL;
}

Also root shall be created only once We should not be change it ever. So change the code like below

if (root == NULL) {  
     root = addHelper(root, value);  
   } else {  
     addHelper(root, value);  
   }  

Answer 3

You don't initialize your root variable before using it. You can initialize it in a constructor as the following:

public:
BST(){
  root = new node();
}