建立二叉树，层序、先序遍历 要求能够输入树的各个结点，并能够输出用不同方法遍历的遍历序列；分别建立建立二叉树存储结构的的输入函数、输出层序遍历序列的函数、输出先序遍历序列的函数；-Establishment of a binary tree, sequence, preorder required to enter each node of the tree, and can output traversal sequences of different methods to traverse