Medium
,Design
,String
,Hash Table
1396. Design Underground System
An underground railway system is keeping track of customer travel times between different stations. They are using this data to calculate the average time it takes to travel from one station to another.
Implement the UndergroundSystem
class:
void checkIn(int id, string stationName, int t)
stationName
at time t
.void checkOut(int id, string stationName, int t)
double getAverageTime(string startStation, string endStation)
startStation
to endStation
.startStation
to endStation
that happened directly, meaning a check in at startStation
followed by a check out from endStation
.startStation
to endStation
may be different from the time it takes to travel from endStation
to startStation
.startStation
to endStation
before getAverageTime
is called.You may assume all calls to the checkIn
and checkOut
methods are consistent. If a customer checks in at time t1
then checks out at time t2
, then t1 < t2
. All events happen 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"]]
Output
[null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000]
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 2:
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"]]
Output
[null,null,null,5.00000,null,null,5.50000,null,null,6.66667]
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
Constraints:
id
, t
<= 106stationName.length
, startStation.length
, endStation.length
<= 10checkIn
, checkOut
, and getAverageTime
.
class UndergroundSystem:
def __init__(self):
self.data = dict()
self.time = defaultdict(lambda: [0, 0])
def checkIn(self, id: int, stationName: str, t: int) -> None:
self.data[id] = stationName, t
def checkOut(self, id: int, stationName: str, t: int) -> None:
startStation, startTime = self.data.pop(id)
time = self.time[startStation, stationName]
time[0] += t - startTime
time[1] += 1
def getAverageTime(self, startStation: str, endStation: str) -> float:
total_time, trips = self.time[startStation, endStation]
return total_time / trips
Yen-Chi ChenWed, May 31, 2023
class UndergroundSystem {
public:
unordered_map<int, pair<string, int>> checkInMap;
unordered_map<string, pair<double, int>> routeMap;
UndergroundSystem() {
}
void checkIn(int id, string startStation, int startTime) {
checkInMap[id] = {startStation, startTime};
}
void checkOut(int id, string dstStation, int dstTime) {
const auto [startStation, startTime] = checkInMap[id];
checkInMap.erase(checkInMap.find(id));
string routeId = startStation + "_" + dstStation;
routeMap[routeId].first += dstTime - startTime;
routeMap[routeId].second ++;
}
double getAverageTime(string startStation, string dstStation) {
string routeId = startStation + "_" + dstStation;
// cout << "(" << routeMap[routeId].first << "," <<routeMap[routeId].second << ")" << endl;
return routeMap[routeId].first / routeMap[routeId].second;
}
};
/**
* Your UndergroundSystem object will be instantiated and called as such:
* UndergroundSystem* obj = new UndergroundSystem();
* obj->checkIn(id,stationName,t);
* obj->checkOut(id,stationName,t);
* double param_3 = obj->getAverageTime(startStation,endStation);
*/
Jerry WuWed, May 31, 2023
public class UndergroundSystem {
Dictionary<int, (string station, int time)> _checkInData = new Dictionary<int, (string station, int time)>();
Dictionary<string, (int time, int count)> _records = new Dictionary<string, (int time, int count)>();
public UndergroundSystem() {}
public void CheckIn(int id, string stationName, int t) {
_checkInData[id] = (stationName, t);
}
public void CheckOut(int id, string stationName, int t) {
if (_checkInData.TryGetValue(id, out var data)) {
string key = $"{data.station}%{stationName}";
int time = t - data.time;
if (_records.TryGetValue(key, out var record)){
_records[key] = (record.time + time, record.count + 1);
} else {
_records[key] = (time, 1);
}
_checkInData.Remove(id);
}
}
public double GetAverageTime(string startStation, string endStation) {
var record = _records[$"{startStation}%{endStation}"];
return (double)record.time / record.count;
}
}
JimJun 1, 2023