自创的算法，输入表达式，建立二叉树的程序，然后输出前缀中缀后缀表示法，利用的对表达式的分割与递归实现输入，同时这也是一个完整的波兰式转换程序，相当稳健-own algorithm, the importation of expression, the establishment of the binary tree and then output the suffix prefix which is made up of the method, using the right expressio