1、　　利用先序遍历和层次遍历的结果建立二叉树

2、　　实现二叉树的层次遍历

3、　　统计二叉树叶子结点的个数（递归）。

4、　　将二叉树左右子树相互交换（递归）

5、　　判断二叉树是不是二叉排序树。

6、　　完成二叉排序树的插入、删除和平衡操作。

-1, the use of first order to traverse and level traversal of the results established binary tree

2 and realize the binary tree level traversal

3, statistical binary leaves the number of nodes (recursion).

4, will binary tree son exchange about tree (recursion)

5, judge binary tree is binary sort tree.

6, complete binary sort tree insert, and delete and balance operation.