← Capital One Interview Insights
The binary search part was fine, I got through it without too much trouble.
First, clarify the problem constraints and edge cases, especially when the current time is before the first departure. Then, explain how binary search can be adapted to find the most recent departure that is <= current time, and finally compute the time difference in minutes.
Pro tip: Mention that if the current time is before the first departure, you should return a sentinel value (e.g., -1) or handle it as a special case, and discuss how this might represent a departure from the previous day if the schedule is daily.
Confirm the input format (e.g., list of times as strings or minutes since midnight), the definition of 'most recent departure that has already passed', and the expected output when no departure has passed.
Discuss the case when the current time is before the first departure: either return a sentinel value or consider the last departure from the previous day if the schedule repeats daily.
Explain how to modify binary search to find the largest departure time less than or equal to the current time. Use a standard binary search but track the best candidate when moving left or right.
Once the departure time is found, calculate the difference in minutes between the current time and that departure time.
State that the binary search approach runs in O(log n) time and O(1) space, and discuss alternative approaches like linear scan and their trade-offs.
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