How i can merge two binary trees

Question

I have two binary trees and I want to merge them. My first question is that whether we can merge two binary trees and if yes how efficiently I can perform the merge operati

Answer 1

Not considering efficiency this answer may work Algorithm of combining two binary trees? . If sorted or balanced, discussion on efficiency in How to merge two BST's efficiently? and Concatenating/Merging/Joining two AVL trees