total_time_insured.py

""" 
A single thread function to get the total amount of time spent being insured.
"""


def get_time_being_insured(intervals) -> float:
    """Get the time being insured"""

    events = []
    for start, end in intervals:
        events.append((start,  1 ))
        events.append((end,   -1 ))

    # Sorting by occurences of events
    # second coordinate distinguishes start (1) from end (0)
    sorted_events = sorted(events, key=lambda x: x[0])

    # now we do a simple line swipe:
    # starting from earliest event till last even.
    # we add up differences between times of consecutive events
    # only if currently we are inside some interval
    opened_intervals = 1 # until current moment excluding it.
    time_insured = 0.0
    
    prev_time, _ = sorted_events[0]

    for time, opening_or_closing_of_interval in sorted_events[1:]:
        if opened_intervals:
            time_insured += time - prev_time
        opened_intervals += opening_or_closing_of_interval
        prev_time = time
        
    return time_insured






if __name__ == "__main__":
    # some small test case

    starts = [10, 30, 20, 50, 100]
    ends   = [24, 59, 26, 52, 105]

    # [10, 24] or [30, 59] or [20, 26] or [50, 52] or [100, 105]
    # =
    # [10, 26] or [30, 59] or [100, 105]

    intervals = list(zip(starts, ends)) # no need for 'list' except printing

    print("Trying to get total time of being insured with intervals:")

    for start, end in intervals:
        print(f"[{start} : {end}]")

    print(f"Expecting interval to span 16 + 29 + 5 = 50")
    print("Getting:")

    print(get_time_being_insured(intervals))