完成非的过程

代码说明：

该程序完成对二叉树的非递归的前序遍历，在三种遍历方法中，这种遍历最简单，所以，核心代码自然要少很多。-completion of the process of non- recursive binary tree of the former preorder, the three traverse method, which traverse the most simple, so natural to the core code is much less.