func validateTree(t *pb.TreeNode) error {
if isLeaf(t) {
if t.GetLeft() != nil || t.GetRight() != nil {
return fmt.Errorf("leaf has non-zero children: %v", t)
}
return nil
}
// not a leaf - must have both children
if t.GetLeft() == nil || t.GetRight() == nil {
return fmt.Errorf("branch has nil children: %v", t.String())
}
err := validateTree(t.GetLeft())
if err != nil {
return err
}
err = validateTree(t.GetRight())
if err != nil {
return err
}
return nil
}
