1 class UndergroundSystem: 2 def __init__(self): 3 self.startStation = collections.defaultdict(lambda: collections.defaultdict(int)) 4 self.endStation = collections.defaultdict(lambda: collections.defaultdict(int)) 5 6 def checkIn(self, id: int, stationName: str, t: int) -> None: 7 self.startStation[stationName][id] = t 8 9 def checkOut(self, id: int, stationName: str, t: int) -> None: 10 self.endStation[stationName][id] = t 11 12 def getAverageTime(self, startStation: str, endStation: str) -> float: 13 time = 0 14 customers = 0 15 for id in self.endStation[endStation]: 16 if id in self.startStation[startStation]: 17 customers += 1 18 time += self.endStation[endStation][id] - self.startStation[startStation][id] 19 20 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：
1 class Station: 2 def __init__(self): 3 self.startStation = '' 4 self.startTime = -1.0 5 self.endStation = '' 6 self.endTime = -1.0 7 8 class UndergroundSystem: 9 10 def __init__(self): 11 self.dic = dict()#以cardid为key 12 13 def checkIn(self, id: int, stationName: str, t: int) -> None: 14 station = Station() 15 station.startStation = stationName 16 station.startTime = t 17 self.dic[id] = station 18 19 def checkOut(self, id: int, stationName: str, t: int) -> None: 20 self.dic[id].endStation = stationName 21 self.dic[id].endTime = t 22 23 def getAverageTime(self, startStation: str, endStation: str) -> float: 24 count = 0 25 sums = 0 26 for id,record in self.dic.items(): 27 if record.startStation == startStation and record.endStation == endStation: 28 count += 1.0 29 sums += float(record.endTime - record.startTime) 30 return round(float(sums) / count, 1) if count != 0 else 0
