用C++语言编写一段程序，该程序的功能相当于一个一元多项式计算器。它能够实现按照指数降序排列建立并输出多项式，并且能够完成两个多项式的相加、相减的运算和将其结果输入的功能。-C++ language with a program that functions as a unary polynomial calculator. It can be achieved in accordance with established and the output index in descending order polynomial, and be able to complete the sum of two polynomials, subtracting the results of operations and will enter the function.