Descr iption 给出一棵孩子兄弟表示法下的树的结构以及各个结点的权值，要求按先序、后序、层次遍历二叉树并输出各个结点的权值。(Descr iption This paper gives the structure of a child's brother representation and the weight of each node, and asks for traversing the two fork tree according to the preorder, po