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

I did it by preorder recurssion. Altough it doesn't exactly follow the interview format by using localRoot, but I think you get the idea.

private int countNodes(Node localRoot, int count) {
    if (localRoot == null) 
        return count;     
    count++; // Visit root
    count = countNodes(localRoot.left, count); // Preorder-traverse (left)
    count = countNodes(localRoot.right, count); // Preorder-traverse (right)
    return count;
}

public int countNodes() {
   return countNodes(root, 0);
}