设计一个Width类，其中包含一个静态数据成员count，用于记录全局存在的Width对象的个数。每次创建一个对象则计数器自动加一，每次销毁时，自动减1。-Width to design a class, which includes a static data member count, used to record the existence of the Width overall number of objects. Every time an object is created aut