User Flight Location Tracker

Find Traveler's Current Airport

Implement solve(flights, queries).

Design a service that answers where a traveler is located at a given UTC moment. You are given flights and a query containing userId and time. For the requested user and timestamp, return the IATA airport code where that user is located.

Each record in flights is a list of five strings in this fixed order:

[departureAirport, departureTime, arrivalAirport, arrivalTime, userId]

• departureAirport and arrivalAirport are IATA codes such as "SFO" or "JFK".
• departureTime and arrivalTime are ISO 8601 UTC datetime strings such as "2021-10-26T16:15:00Z".
• userId is a numeric user identifier stored as a string.

Location is determined by these rules:

1. For a user with no flights, return "".
2. If time comes before that user's first departureTime, return the first flight's departureAirport.
3. If the query time falls within an active flight, meaning departureTime[i] <= time < arrivalTime[i], return "".
4. If the query time falls on the ground after one flight and before the next, meaning arrivalTime[i] <= time < departureTime[i + 1], return arrivalAirport[i].
5. If the query time is at or after the last arrivalTime, return that final arrivalAirport.

Example 1:

Input:
flights = [["SFO", "2021-10-26T16:15:00Z", "JFK", "2021-10-26T21:34:00Z", "1"],
           ["JFK", "2021-10-29T18:31:00Z", "MIA", "2021-10-29T21:36:00Z", "1"],
           ["MIA", "2021-11-15T15:10:00Z", "MSY", "2021-11-15T18:21:00Z", "1"],
           ["SFO", "2021-10-28T11:47:00Z", "SEA", "2021-10-28T14:02:00Z", "2"],
           ["SEA", "2021-11-04T03:47:00Z", "JFK", "2021-11-04T09:12:00Z", "2"]]
userId = 1
time = "2021-10-26T15:00:00Z"

Output: "SFO"

Explanation: At 15:00 UTC, user 1's first flight has not yet departed from SFO, so the traveler is still at the departure airport.

Example 2:

Input:
flights = [["BOS", "2023-01-05T06:00:00Z", "DFW", "2023-01-05T10:00:00Z", "2"], ["DFW", "2023-01-08T12:00:00Z", "SEA", "2023-01-08T15:00:00Z", "2"]]
userId = 2
time = "2023-01-06T12:00:00Z"

Output: "DFW"

Example 3:

Input:
flights = [["SFO", "2021-10-26T16:15:00Z", "JFK", "2021-10-26T21:34:00Z", "1"]]
userId = 99
time = "2021-10-26T15:00:00Z"

Output: ""

Constraints:

• 1 <= flights.size() <= 10^5
• Every flight record has exactly 5 strings.
• Every userId is a positive integer between 1 and 10^9.
• For every flight, departureTime < arrivalTime.
• For each user, after sorting flights by departureTime, flight intervals do not overlap.