Counting nodes in a tree in Java

Question

First of all, I swear this is not homework, it\'s a question I was asked in an interview. I think I made a mess of it (though I did realise the solution requires recursion).

Answer 1

This is a standard recursion problem:

count():
    cnt = 1 // this node
    if (haveRight) cnt += right.count
    if (haveLeft)  cnt += left.count
return cnt;

Very inefficient, and a killer if the tree is very deep, but that's recursion for ya...