Merging binaries trees into another one

[thames]

Good evening. I'm studying merging of two binaries trees and I was concerned about two instructions:

bitree_root(merge)->left = bitree_root(left);
bitree_root(merge)->right = bitree_root(right);

I would like to know if merging two binaries trees means to create one of the subtrees as the left node of the new (merged) binary tree and the other as the right node of it.

Like this (please toggle to plain text):

        root of merged tree
           /             \ 
          /               \ 
left subtree           right subtree

 
int bitree_merge(BiTree *merge, BiTree *left, BiTree *right, const void
   *data) {

/*****************************************************************************
*                                                                            *
*  Initialize the merged tree.                                               *
*                                                                            *
*****************************************************************************/

bitree_init(merge, left->destroy);

/*****************************************************************************
*                                                                            *
*  Insert the data for the root node of the merged tree.                     *
*                                                                            *
*****************************************************************************/

if (bitree_ins_left(merge, NULL, data) != 0) {

   bitree_destroy(merge);
   return -1;

}

/*****************************************************************************
*                                                                            *
*  Merge the two binary trees into a single binary tree.                     *
*                                                                            *
*****************************************************************************/

bitree_root(merge)->left = bitree_root(left);
bitree_root(merge)->right = bitree_root(right);

/*****************************************************************************
*                                                                            *
*  Adjust the size of the new binary tree.                                   *
*                                                                            *
*****************************************************************************/

merge->size = merge->size + bitree_size(left) + bitree_size(right);

/*****************************************************************************
*                                                                            *
*  Do not let the original trees access the merged nodes.                    *
*                                                                            *
*****************************************************************************/

left->root = NULL;
left->size = 0;
right->root = NULL;
right->size = 0;

return 0;

}