isEmpty empty true isEmpty node l r false left empty empty left node l r l right empty empty right node l r r inc 0 s 0 inc s x s inc x count n x if isEmpty n isEmpty left n right n node left left n node right left n right n x inc x if true b n m x y x if false false n m x y count m x if false true n m x y count n y nrOfNodes n count n 0 isEmpty 1 empty 0 true 0 node 2 false 0 left 1 right 1 inc 1 0 0 s 1 count 2 if 6 nrOfNodes 1 FULL ./TRS/secret06/aprove/nrOfNodes.trs