二叉排序树：又称二叉查找树。 它或者是一棵空树；或者是具有下列性质的二叉树： （1）若左子树不空，则左子树上所有结点的值均小于它的根结点的值； （2）若右子树不空，则右子树上所有结点的值均大于它的根结点的值； （3）左、右子树也分别为二叉排序树；-Binary sort tree: also known as binary search tree. Or an empty tree　or a binary tree with the following properties: (1) If the left subtree is not empty, then the value of all the nodes of the left subtree are less than the value of its root　(2) If the right subtree is not empty, then the right sub-tree node values ​ ​ are greater than the value of its root　(3) left and right subtree respectively, binary sort tree