Question: Draw all the nonisomorphic trees with four nodes.
Two trees are isomorphic if there is a bijection f: N1 → N, where f maps the root of one tree to the root of the other and where f(y) is a child of f(x) in the second tree when y is a child of x in the first tree. Thus the two trees shown are isomorphic graphs but not isomorphic trees (in part (a) the root has two children and in part (b) it does not). These are the only two nonisomorphic trees with three nodes.
