Build a Progressive Employee Tracker

Problem Statement

Design an in-memory employee attendance and payroll management class, EmployeeTracker. The system tracks employee shifts, hourly rates, promotions, global bonus intervals, and total time worked.

Implement the EmployeeTracker class with the following methods:

• register_employee(emp_id: str, initial_hourly_rate: float) -> None: Registers a new employee with a base hourly rate.

• schedule_promotion(emp_id: str, effective_time: int, new_hourly_rate: float) -> None: Schedules a rate update for emp_id. The promotion takes effect at the employee's first clock-in at or after effective_time. An ongoing shift active across effective_time is not affected; its rate remains snapshotted at its initial clock-in rate.

• add_bonus_window(start_time: int, end_time: int) -> None: Adds a global bonus window [start_time, end_time). Any portion of a shift overlapping with one or more bonus windows is paid at 2.0x the shift's snapshotted rate. Overlapping or contiguous bonus windows must be merged so bonus pay is applied at most once per time unit.

• clock_in(emp_id: str, timestamp: int) -> None: Clocks in an employee. Applies any scheduled promotions whose effective_time None: Clocks out the employee, closing the shift [clock_in_time, timestamp). Accrues total completed duration and earned pay.

• get_total_pay(emp_id: str) -> float: Returns total earnings from all closed shifts for the employee. Returns 0.0 if no shifts have been closed.

• get_top_k_worked(k: int) -> list[str]: Returns the emp_ids of the top k employees by total closed shift duration in descending order. Break ties lexicographically by emp_id in ascending order.

All timestamps and durations are integers representing hours.

Constraints

• Timestamps are non-negative integers (0 <= timestamp <= 10^9).
• Calls to clock_in and clock_out for any given employee are guaranteed to be strictly valid (alternating, non-empty, and strictly increasing timestamps).
• Bonus windows satisfy 0 <= start_time < end_time <= 10^9.
• At most 10^5 operations across all methods.

Example

tracker = EmployeeTracker()
tracker.register_employee("E1", 20.0)
tracker.add_bonus_window(2, 5)
tracker.add_bonus_window(4, 7)  # Merged window: [2, 7)

tracker.clock_in("E1", 1)
tracker.clock_out("E1", 4)
# Shift [1, 4): duration 3 hours.
# Overlap with [2, 7) is [2, 4) (2 hrs). Normal portion: [1, 2) (1 hr).
# Pay: (1 hr * 20.0) + (2 hrs * 20.0 * 2.0) = 20.0 + 80.0 = 100.0

tracker.schedule_promotion("E1", 5, 30.0)
tracker.clock_in("E1", 6)
# Timestamp 6 >= 5, so rate is updated to 30.0 for this shift.
tracker.clock_out("E1", 9)
# Shift [6, 9): duration 3 hours.
# Overlap with [2, 7) is [6, 7) (1 hr bonus). Normal portion: [7, 9) (2 hrs).
# Pay: (1 hr * 30.0 * 2.0) + (2 hrs * 30.0) = 60.0 + 60.0 = 120.0

assert tracker.get_total_pay("E1") == 220.0
assert tracker.get_top_k_worked(1) == ["E1"]