Recursion stack in Binary search tree

Question

I am trying to delete a node from a binary search tree. While this function works properly why do we need to set node->m_left or node->m_right to return value of deletenode function itself? It is hard to understand this recursive structure.
currently doing it only for the leaf node

Node<T>*  deletenode(T key){
         return deletenode(key,this->root);
        }
        Node<T>*  deletenode(T key,Node<T>* node){
            Node<T>* temp;
         if(node==nullptr){
             return node;
         }
         if(key<node->m_data){
             node->m_left=deletenode(key,node->m_left);
         }
         if(key>node->m_data){
             node->m_right=deletenode(key,node->m_right);
         }
          
         

         return temp;
        }
        
        

Answer 1

You're setting the left or right to the result of calling the deletenode function on that branch, not to the function itself.

The recursion means: "If my tree has a left branch and a right branch, and the item to delete is in the left branch, then make a new tree that has the same right branch, but the result of removing the item to delete from the left branch as its left branch"