简单多项式的树结构表示方法，四则运算以及求导运算.-Simple tree structure representation of polynomials, arithmetic and derivative operations.

本程序是数据结构作业之一，实现了多项式的四则运算，并将结果显示在控制事台上。-This program is one of the jobs of a data structure, polynomial arithmetic, and display the results in control of things on stage.