无序的顺序表实现一个城市数据库。① 用列表对城市进行记录和管理，实现城市的增加、删除和查询功能，并实现文件保存和读取

② 计算城市之间距离，统计输出距离某城市一定范围内的所有城市。

③ 实现一定规模城市的遍历最佳路径选择。-Unordered sequence table to implement a city database. ① list of cities with records and management, increase of the city, delete, and query functions, and save the file and read ② calculate the distance between cities, all cities within a certain range of statistical output from the city. ③ Choose the best path to achieve a certain scale to traverse the city.