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

A simple enumeration (in any deterministic order) together with a hash function that depends when the node is visited should work.

int hash(Node root) {
  ArrayList worklist = new ArrayList();
  worklist.add(root);
  int h = 0;
  int n = 0;
  while (!worklist.isEmpty()) {
    Node x = worklist.remove(worklist.size() - 1);
    worklist.addAll(x.children());
    h ^= place_hash(x.hash(), n);
    n++;
  }
  return h;
}

int place_hash(int hash, int place) {
  return (Integer.toString(hash) + "_" + Integer.toString(place)).hash();
}