Hashing a Tree Structure

Question

I\'ve just come across a scenario in my project where it I need to compare different tree objects for equality with already known instances, and have considered that some so

Answer 1

I think you could do this recursively: Assume you have a hash function h that hashes strings of arbitrary length (e.g. SHA-1). Now, the hash of a tree is the hash of a string that is created as a concatenation of the hash of the current element (you have your own function for that) and hashes of all the children of that node (from recursive calls of the function).

For a binary tree you would have:

Hash( h(node->data) || Hash(node->left) || Hash(node->right) )

You may need to carefully check if tree geometry is properly accounted for. I think that with some effort you could derive a method for which finding collisions for such trees could be as hard as finding collisions in the underlying hash function.