The complexity constraints were printed right there in the problem and i still fumbled around for a bit before realizing there was nothing clever to do.
Start by clarifying requirements and constraints, then propose a design using a hash map for O(1) driver registration and pay computation, with a running total updated on each shift. Implement a Driver class storing hourly wage and a PayrollSystem managing drivers and total payout, ensuring all operations are constant time.
Pro tip: Mention that O(1) pay computation assumes the shift duration is computed from timestamps in constant time, and highlight that the running total is updated incrementally to avoid O(n) aggregation. Also, discuss edge cases like overlapping shifts or negative durations to show thoroughness.
Ask about expected input formats, whether shifts can overlap, if wages can change, and if the running total should be per driver or global. Confirm that O(1) is required for registration and pay computation.
Use a hash map (dictionary) to store drivers by ID for O(1) registration and lookup. Each driver object stores hourly wage and optionally a running total of their own pay. Maintain a global running total as a variable.
For registration, insert into the hash map. For pay computation, calculate duration as (end - start) in hours, multiply by wage, add to driver's total and global total, and return the pay. All operations are O(1).
Discuss handling invalid timestamps (end < start), zero-duration shifts, and concurrent updates. Mention that O(1) assumes no need to aggregate across drivers for each computation, and that the running total is updated incrementally.
Walk through a simple example: register driver with wage, compute pay for a shift, verify running total. Suggest unit tests for edge cases and performance tests to confirm O(1).
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