leetcode

design-underground-system.dart (1772B)

---

 //This theoretically has an issue, but in
 //reality the issue is with the question and not my implementation
 //thus I consider this correct as it does what is expected
 //which is tracking entry and exit and finding the average time
 //for a single hop between the two.
 
 //To solve this I created a trip class which just stores where
 //a given user started and at what time. This is placed as the value
 //for the key which is the user's id.
 //Then from here when the user leaves you take the end time - start time
 //and add it to the total time to travel from one station to another along with
 //iterating the total number of trips by 1 to be able to find the mean.
 
 class UndergroundSystem {
   Map<int, Trip> travelling_users = {};
   Map<String, List<int>> trip_times = {};
 
   void checkIn(int id, String stationName, int t) {
       if(travelling_users.containsKey(id)){
           return;
       }
       travelling_users[id] = new Trip( stationName,t);
   }
   
   void checkOut(int id, String stationName, int t) {
       Trip current_trip = (travelling_users[id] ?? new Trip('',0));
       String locations = current_trip.start_name + " " + stationName;
       List<int> this_trip_time = (trip_times[locations] ?? [0,0]);
       this_trip_time[0] += 1;
       this_trip_time[1] += t - current_trip.start_time;
       trip_times[locations] = this_trip_time;
   }
   
   double getAverageTime(String startStation, String endStation) {
       List<int> spec_trip = (trip_times[startStation + " " + endStation] ?? []);
       double average = spec_trip[1] / spec_trip[0];
       return average;
   }
 }
 
 
 class Trip{
     String start_name = "";
     int start_time = 0;
     Trip(String _start_name, int _start_time){
         start_name = _start_name;
         start_time = _start_time;
     }
 
 }