建立二叉树，统计二叉树中度为2的结点个数和叶子结点个数（ 用递归或非递归的方法都可以，先序、中序或后序均可）-establish binary tree, Statistics for the two binary tree to moderate the number of nodes and the number of nodes leaves (with the recursive and non - recursive method can be first order, After the order or sequence may)