#1396

Design Underground System

pupil · 500 · lc medium +27 · 74.4% accepted · 3,586 likes · top 85%

Description

A subway system tracks trip times between stations to compute averages. Implement the UndergroundSystem class:

- void checkIn(int id, string stationName, int t)

- Customer id enters stationName at time t. Each customer can be checked in at only one station at a time.

- void checkOut(int id, string stationName, int t)

- Customer id exits stationName at time t.

- double getAverageTime(string startStation, string endStation)

- Returns the mean travel time over all completed direct journeys from startStation to endStation.

- The average covers only direct trips (check-in at start, check-out at end).

- Travel time from A to B may differ from B to A.

- At least one journey from startStation to endStation will exist before this is called.

All checkIn and checkOut calls are consistent (t1 < t2) and arrive in chronological order.

Example 1:

Input

["UndergroundSystem","checkIn","checkIn","checkIn","checkOut","checkOut","checkOut","getAverageTime","getAverageTime","checkIn","getAverageTime","checkOut","getAverageTime"]

[[],[45,"Leyton",3],[32,"Paradise",8],[27,"Leyton",10],[45,"Waterloo",15],[27,"Waterloo",20],[32,"Cambridge",22],["Paradise","Cambridge"],["Leyton","Waterloo"],[10,"Leyton",24],["Leyton","Waterloo"],[10,"Waterloo",38],["Leyton","Waterloo"]]

Example 2:

Output

[null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000]

Example 3:

Explanation

UndergroundSystem undergroundSystem = new UndergroundSystem();

undergroundSystem.checkIn(45, "Leyton", 3);

undergroundSystem.checkIn(32, "Paradise", 8);

undergroundSystem.checkIn(27, "Leyton", 10);

undergroundSystem.checkOut(45, "Waterloo", 15); // Customer 45 "Leyton" -> "Waterloo" in 15-3 = 12

undergroundSystem.checkOut(27, "Waterloo", 20); // Customer 27 "Leyton" -> "Waterloo" in 20-10 = 10

undergroundSystem.checkOut(32, "Cambridge", 22); // Customer 32 "Paradise" -> "Cambridge" in 22-8 = 14

undergroundSystem.getAverageTime("Paradise", "Cambridge"); // return 14.00000. One trip "Paradise" -> "Cambridge", (14) / 1 = 14

undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000. Two trips "Leyton" -> "Waterloo", (10 + 12) / 2 = 11

undergroundSystem.checkIn(10, "Leyton", 24);

undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000

undergroundSystem.checkOut(10, "Waterloo", 38); // Customer 10 "Leyton" -> "Waterloo" in 38-24 = 14

undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 12.00000. Three trips "Leyton" -> "Waterloo", (10 + 12 + 14) / 3 = 12

Example 4:

Input

["UndergroundSystem","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime"]

[[],[10,"Leyton",3],[10,"Paradise",8],["Leyton","Paradise"],[5,"Leyton",10],[5,"Paradise",16],["Leyton","Paradise"],[2,"Leyton",21],[2,"Paradise",30],["Leyton","Paradise"]]

Example 5:

Output

[null,null,null,5.00000,null,null,5.50000,null,null,6.66667]

Example 6:

Explanation

UndergroundSystem undergroundSystem = new UndergroundSystem();

undergroundSystem.checkIn(10, "Leyton", 3);

undergroundSystem.checkOut(10, "Paradise", 8); // Customer 10 "Leyton" -> "Paradise" in 8-3 = 5

undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.00000, (5) / 1 = 5

undergroundSystem.checkIn(5, "Leyton", 10);

undergroundSystem.checkOut(5, "Paradise", 16); // Customer 5 "Leyton" -> "Paradise" in 16-10 = 6

undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.50000, (5 + 6) / 2 = 5.5

undergroundSystem.checkIn(2, "Leyton", 21);

undergroundSystem.checkOut(2, "Paradise", 30); // Customer 2 "Leyton" -> "Paradise" in 30-21 = 9

undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 6.66667, (5 + 6 + 9) / 3 = 6.66667

Code

class UndergroundSystem:

    def __init__(self):
        

    def checkIn(self, id: int, stationName: str, t: int) -> None:
        

    def checkOut(self, id: int, stationName: str, t: int) -> None:
        

    def getAverageTime(self, startStation: str, endStation: str) -> float:
        


# Your UndergroundSystem object will be instantiated and called as such:
# obj = UndergroundSystem()
# obj.checkIn(id,stationName,t)
# obj.checkOut(id,stationName,t)
# param_3 = obj.getAverageTime(startStation,endStation)

class UndergroundSystem:

    def __init__(self):
        

    def checkIn(self, id: int, stationName: str, t: int) -> None:
        

    def checkOut(self, id: int, stationName: str, t: int) -> None:
        

    def getAverageTime(self, startStation: str, endStation: str) -> float:
        


# Your UndergroundSystem object will be instantiated and called as such:
# obj = UndergroundSystem()
# obj.checkIn(id,stationName,t)
# obj.checkOut(id,stationName,t)
# param_3 = obj.getAverageTime(startStation,endStation)