建立一棵二叉排序树并对它进行前序遍历。建立二叉树利用了插入算法，数据由用户输入；对二叉树前序遍历，利用非递归调用子程序，然后对二叉树（1）访问根结点；（2）遍历左子树；（3）遍历右子树。程序中要注意左右指针llink和rlink的使用。-Create a binary sort tree and pre-order traversal. The establishment of the binary tree to the use of the insertion algorithm, the data entered by the user　binary tree traversal, the use of non-recursive call to a subroutine, then the binary tree (1) access to the root　(2) traverse the left subtree　(3) traverse the right subtree. The program should pay attention to the use of left and right pointers llink and rlink.