How to insert element in binary tree by recursion?

Question

void Btree<T>::InsertNode2(T data, BtreeNode* root)
{
    if (root==NULL)
    {
        root = new BtreeNode (data);
        return ;
    }
    if (data <= root->data)
        InsertNode2(data, root->leftchild);
    else
        InsertNode2(data, root->rightchild);
}

Why isn't it right? The root can't be assigned correctly. After calling the function it's still NULL.

Consider if you are passing root by value or reference, depending on your language. See: http://stackoverflow.com/questions/32492184/binary-tree-root-is-null — DragonMoon, Apr 12 '17 at 15:10

score 0 · Accepted Answer · answered Apr 12 '17 at 18:14

It almost correct. Just, as said by @DragonMoon, all you need to do is to pass root by reference

void Btree<T>::InsertNode2(T data, BtreeNode &* root)
{
    if (root==NULL)
    {
        root = new BtreeNode (data);
        return ;
    }
    if (data <= root->data)
        InsertNode2(data, root->leftchild);
    else
        InsertNode2(data, root->rightchild);
}

How to insert element in binary tree by recursion?

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