class UndergroundSystem:
def __init__(self):
self.data = {}
self.pending = {}
def checkIn(self, id: int, stationName: str, t: int) -> None:
self.pending[id] = [stationName, t]
def checkOut(self, id: int, stationName: str, t: int) -> None:
prevStation = self.pending[id][0]
prevTime = self.pending[id][1]
diff = t - prevTime
if (prevStation, stationName) in self.data:
data = self.data[(prevStation, stationName)]
newCount = data[0] + 1
total = data[1] + diff
self.data[(prevStation, stationName)] = [newCount, total]
else:
self.data[(prevStation, stationName)] = [1, diff]
def getAverageTime(self, startStation: str, endStation: str) -> float:
return self.data[(startStation, endStation)][1] / self.data[(startStation, endStation)][0]
