Question

I hate recursion, I can’t trace through the code easily, but with trees I don’t have a choice.

This is what I’ve tried so far.

private int evaluate(Node n)
{
    if (n != null)
    {
        if (n.isLeaf())  // n is a node with a number
            return Integer.parseInt(n.element);
        else
        {
            int left = evaluate(n.left);
            int right = evaluate(n.right);
            return calculate(left, n.element, right);
        } //end else
    } //end if
} //end evaluate

Answer 1

Do you mean:

return calculate(left, n.element, right);

I assume your node is an operation, ie “+”, “-” etc.

Your “calculate” has to execute the corresponding operation on the int “left” and “right” and you are done!