The tie-break logic is where most people probably trip up.
Model the problem as a discrete event simulation where each person's arrival time is processed in chronological order, and a gate state tracks the last action and time. Use a priority queue to handle simultaneous arrivals, applying the tie-break rules based on the previous moment's action to determine the order of processing. For each person, compute their actual clearance time as the maximum of their arrival time and the next available time slot, updating the gate state accordingly.
Pro tip: Clarify the tie-break rules upfront and consider edge cases like multiple people arriving at the same time with mixed actions; explicitly state your assumptions to avoid ambiguity. Also, discuss the time and space complexity trade-offs of your approach, showing awareness of scalability.
Restate the problem in your own words, confirm the tie-break rules, and identify input/output formats. Ask clarifying questions about edge cases such as empty arrays or invalid actions.
Choose a priority queue to process events in chronological order, and maintain a gate state (last action, last time) to apply tie-break rules. Consider using a map from person ID to their arrival time and action.
Iterate through events in order, grouping simultaneous arrivals. For each group, sort according to tie-break rules, then assign each person the next available time slot, updating the gate state after each assignment.
Implement the specific tie-break rules based on the previous moment's action. Test with cases like all entering, all exiting, alternating, and mixed simultaneous arrivals.
Discuss the time complexity (O(n log n) due to sorting/priority queue) and space complexity (O(n)). Suggest potential optimizations if needed, such as using counting sort for bounded timestamps.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.