1．创建以二叉链表作存储结构的二叉树；

2．按前序遍历二叉树；

3．按中序遍历二叉树；

4．按后序遍历二叉树；

5．计算二叉树的单枝结点数；

6．按层次遍历二叉树。

-1. Create a list binary tree structure for storage　2. According to pre-order tree traversal　3. According to the binary tree traversal　4. After the tree traversal by　5. Calculation of single-branch tree nodes　6. According to the level of binary tree traversal.