An underground railway system tracks customer travel times between stations.
Implement the UndergroundSystem class:
void checkIn(int id, String stationName, int t)void checkOut(int id, String stationName, int t)double getAverageTime(String startStation, String endStation)— returns the average time for the route.
Example:
checkIn(45,"Leyton",3), checkOut(45,"Waterloo",15), getAverageTime("Leyton","Waterloo")→12.0