说明：  一、二叉排序树的查找 ? 二叉排序树的查找可以用递归来实现； ? 先将要查找的关键字和根节点进行比较; ? 若和根节点值相同，则返回根节点值；若比根节点小，就递归查找左子树，若比根节点大，则递归查找右子树
(Searching for the first and second sort trees The search of binary sort tree can be realized by recursion; First, compare the keyword to be found with the root node; if it is the same as the root node, return the root node value; if it is smaller than the root node, recursively search the left subtree; if it is larger than the root node, recursively search the right subtree)