Determine if two binary trees are equal

Question

What would be the efficient algorithm to find if two given binary trees are equal - in structure and content?

Answer 1

I would write it as follows. The following code will work in most functional language, and even in python if your datatypes are hashable (e.g. not dictionaries or lists):

• topological equality (same in structure, i.e. Tree(1,Tree(2,3))==Tree(Tree(2,3),1)):

  tree1==tree2 means set(tree1.children)==set(tree2.children)

• ordered equality:

  tree1==tree2 means tree1.children==tree2.children

(Tree.children is an ordered list of children)

You don't need to handle the base cases (leaves), because equality has been defined for them already.