Why is it wrong to assign NULL values to Node in this code?

help
,
1

I am practicing binary trees from leet code and encountered this error while solving a question
error message:

0xbebebebebebebebe: note: pointer points here
<memory cannot be printed>
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior prog_joined.cpp:41:18

On the internet , i found that it usually happens when we don’t allocate memory to left or right pointers and simply assign the value NULL to them.

can someone tell me why is it wrong to do this and what changes should i make in below code to correct it?

CODE

class Solution {
public:
    void preOrderTraversal(TreeNode* root,queue<TreeNode*> &st)
    {
        if(!root)
            return;
        
        st.push(root);
        preOrderTraversal(root->left,st);
        preOrderTraversal(root->right,st);
        
        return;
    }
    void flatten(TreeNode* root) {
       queue<TreeNode*> st;
       preOrderTraversal(root,st);
        TreeNode* temp=st.front();
        st.pop();
       while(!st.empty())
       {
           temp->left=NULL;
           auto rightNode=st.front();
           st.pop();
           temp->right=rightNode;
           temp=temp->right;
       }
        
    }
};

Problem LInk:-

2

Did you try using nullptr instead of NULL?

Edit: It looks like you’re not handling the case when \text{root} itself is \text{NULL}.

3

and here i was debugging the recursive function for 1 hr :cry: :cry: :cry: :cry: