1396. Design Underground System

https://leetcode.com/problems/design-underground-system/
Python

from collections import defaultdict


class UndergroundSystem:

    def __init__(self):
        self.traveling = dict()
        self.mapper = defaultdict(list)

    def checkIn(self, id: int, stationName: str, t: int) -> None:
        if id in self.traveling:
            # Duplicate check-in
            return

        self.traveling[id] = (stationName, t)


    def checkOut(self, id: int, stationName: str, t: int) -> None:
        if id not in self.traveling:
            # Traveler not checked-in
            return

        in_station, in_t = self.traveling.pop(id)
        out_station, out_t = stationName, t

        self.mapper[(in_station, out_station)].append(out_t - in_t)

    def getAverageTime(self, startStation: str, endStation: str) -> float:
        if (startStation, endStation) not in self.mapper:
            # No data
            return

        time_list = self.mapper[(startStation, endStation)]
        return sum(time_list) / len(time_list)


# 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)
Python​

Python
