leetcode1396

class UndergroundSystem:
    def __init__(self):
        self.startStation = collections.defaultdict(lambda: collections.defaultdict(int))
        self.endStation = collections.defaultdict(lambda: collections.defaultdict(int))

    def checkIn(self, id: int, stationName: str, t: int) -> None:
        self.startStation[stationName][id] = t
        
    def checkOut(self, id: int, stationName: str, t: int) -> None:
        self.endStation[stationName][id] = t
        
    def getAverageTime(self, startStation: str, endStation: str) -> float:
        time = 0
        customers = 0
        for id in self.endStation[endStation]:
            if id in self.startStation[startStation]:
                customers += 1
                time += self.endStation[endStation][id] - self.startStation[startStation][id]
        
        return time / customers if time else 0 

参考：https://leetcode.com/problems/design-underground-system/discuss/554871/Python3-Easy-Python-with-dict

我自己的代码是下面的，第51个testcase，总是通不过，不知道是float的精度问题还是数值计算的不对：

class Station:
    def __init__(self):
        self.startStation = ''
        self.startTime = -1.0
        self.endStation = ''
        self.endTime = -1.0

class UndergroundSystem:

    def __init__(self):
        self.dic = dict()#以cardid为key

    def checkIn(self, id: int, stationName: str, t: int) -> None:
        station = Station()
        station.startStation = stationName
        station.startTime = t
        self.dic[id] = station

    def checkOut(self, id: int, stationName: str, t: int) -> None:
        self.dic[id].endStation = stationName
        self.dic[id].endTime = t

    def getAverageTime(self, startStation: str, endStation: str) -> float:
        count = 0
        sums = 0
        for id,record in self.dic.items():
            if record.startStation == startStation and record.endStation == endStation:
                count += 1.0
                sums += float(record.endTime - record.startTime)
        return round(float(sums) / count, 1) if count != 0 else 0