多元树的层次遍历、先根遍历、后根遍历

问题的描述：

函数填空：层次遍历多元树（在文件tree.cpp中3个空）、先根遍历、后根遍历的递归函数（在文件tree.h中2个空）；

多元树的输入：在主程序中调用多元树的函数（定位根、找大儿子、找下一个兄弟等），输入某棵多元树。

-Multi-level tree traversal, the first traversal the root, root traversal issues Descr iption: function to fill in the blank: multi-level tree traversal (tree.cpp in the document in three space), the first traversal the root, root ergodic recursive function (in the document in two empty tree.h)　multiple input tree: In the main program to call multi-tree function (positioning root, look for the eldest son, to find a brother, etc.), enter a multi-tree tree.