说明：  H11增强Polynomial类 (1) 以动态数组实现多项式类。多项式系数的最大上限为int数据类型能表示的最大整数，但在构建对象时不指定系数上限 (2) 对两个Polynomial类对象的运算，分别重载“+”“-”运算，并能够级联调用 (3) 重载“<<”操作符，并能级联调用。 (4) 重载赋值运算符“=”，思考为何必须重载该运算符，如果不重载会发生什么问题？
(H11 Enhanced the Polynomial class (1) dynamic array polynomial class. The maximum upper limit of the polynomial coefficients int data type can represent the largest integer, but do not specify when the object is to build the upper limit of the coefficient (2) of two Polynomial class object computing, reload+ " -" operator, and be able to level joint call to (3) " < < " operator is overloaded and can be cascaded call. (4) The overloaded assignment operator " =" , think about why it is necessary to override the operator, what happens if you do not reload?)