I'm new in binary tree, i want to traverse the 2 node in the binary tree but the output result into a random number or no output.

Here's the driver function:

int main(){
   node *root, *num2;

   bt tree;

   root = new node;
   root->data = 12;
   root->left = num2;
   root->right = NULL;

   tree.root = root;

   num2 = new node;
   num2->data = 10;
   num2->right = NULL;
   num2->left =NULL;

   std::cout<<"Postorder: ";
   tree.postorder();
   std::cout<<"\n";

   return 0;
}

Binary traversal methods:

struct bt{
    node *root = nullptr;

    public:
        void postorder(){
            postorder_impl(root);
        }
        
        
    private:
        void postorder_impl(node *start){
            if(!start) return;
            postorder_impl(start->left);
            postorder_impl(start->right);
            std::cout << start->data <<  " ";
        }
    
};

CodePudding user response：

When you write root->left = num2; num2 is uninitalized yet. So it is a random adres in memory. So root->left (and start->left inside the postorder(); function). So you will call the postorder_impl(); function with an undefined adress will be is a random memoryadres even after you set num2 to a valid node.

Put num2 = new node; before it. root->left = num2;