The problem statement itself takes a while to parse.
Model the problem as a discrete event simulation where at each time step you determine which person uses the door based on the priority rules. Use two queues (enter and exit) to manage waiting people, and track the door's last direction to apply tie-breaking. Iterate through time, processing arrivals and selecting the next person according to the rules until all are served.
Pro tip: Clarify edge cases upfront, such as simultaneous arrivals and the initial idle state, to ensure your solution handles all scenarios correctly. Also, consider using a priority queue or sorting arrivals by timestamp to efficiently process events in chronological order.
Parse the input into a list of events with timestamp, direction, and index. Use two queues (or lists) to represent waiting people for each direction, and maintain variables for current time and last direction.
At each time unit, add any new arrivals to the appropriate queue. Then, if the door is free, select the next person based on priority: if both queues non-empty, use last direction (or exit if idle); otherwise pick from the non-empty queue.
When multiple people are waiting in the same direction, always choose the one with the lowest index (earliest arrival). This ensures fairness as specified.
Assign the current time as the usage time for the selected person, remove them from the queue, update last direction, and increment time. Continue until all people have used the door.
Output the usage times for each person in the original order (by index). Verify with small test cases to ensure correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.