设计一个交通咨询系统，能让旅客咨询从任一个城市顶点到另一个城市顶点之间的最短路径（里程）或最低花费或最短时间等问题。对于不同咨询要求，可输入城市间的路程或所需时间或所需费用。-Design a traffic advisory system, can let passengers from a city of consulting the vertices to another city between vertices of the shortest path (mileage) or the