二叉树的递归算法：计算高度、结点个数、交换左右儿子
问题的描述
写一完整函数，计算树的结点数目int CountNode(BTNode<T>* &t)；
完善以下两个函数：
计算树的高度int Depth(BTNode<T>* &root)；
对树的所有子树交换左右孩子void swapsons(BTNode<T>* &t)；,Binary Tree Recursive Algorithm: Calculate the height of node number, the exchange about the issue of his son to write a complete descr iption of function, calculating the number of tree node int CountNode (BTNode