迭代地将新节点添加到二叉树中，根被覆盖

Question

I found the needed code to iteratively add new nodes, though it doesn't work in my case.

 // bal=left  jobb=right
void bkf::beszur(int k) {
    if(root != NULL) 
        while (true) {
            if (k < root->data) {
                if (root->bal == NULL) {
                    root->bal = new node;
                    root->bal->data = k;
                    root->bal->bal = NULL;
                    root->bal->jobb = NULL;
                    break;
                }
                else
                    root = root->bal;   // overwrites root
            }
            else 
                if (root->jobb == NULL) {
                    root->jobb = new node;
                    root->jobb->data = k;
                    root->jobb->bal = NULL;
                    root->jobb->jobb = NULL;
                    break;
                } else 
                    root = root->jobb;   // overwrites root
        }
    else {
        root = new node;
        root->data = k;
        root->bal = NULL;
        root->jobb = NULL;
    }
}

At "root = root->bal" the root gets overwritten, so so it takes the data and left and right node of root->bal too. I also tried creating a "node *p", and assigning root to it, but that way it allocates memory for p itself, not where p is pointing to. Here's the declaration:

struct node {
    int data;
    node *bal;
    node *jobb;
};

class bkf {
    node *root;
    // ...

How is this done properly?

Answer 1

Maybe the point is that you don't store your root node before doing the traversing/inserting inside the tree. Hence root is an arbitrary node after calling the function.

Maybe you should store the root before first function call to always have the entry point to start again.

Answer 2

Because root is the class level scope variable. Make a local copy of root, let's say root_local.

root_local = root.

And then start using it in the function.

when you do the root = root->bal. root is changed at class level.