Hi, everyone, I disagree with the provided answer to the BONUS part of the challenge and respectfully submit my own. Two reasons:
- Look closely at the data. You will find that all 12 ship transits associated with the answer occur at exactly the same time (14:30 on August 30th, 2015) with different vessels (CV20, CV21, CV22...CV31). I don't know exactly what it means (maybe it was a bunch of barges tied together like we have in US rivers? Or maybe a whole flotilla like in a parade?) Either way I don't think the bridge went up and down 12 times. This pattern, multiple ships passing at the same time, is widespread in the data.
- The answer provided conflates the date with the day of the week. Of course, the day of the week for a particular date varies from year to year, and it seems to me the question is about the best day of the week and time of day to go looking, not an ordinal day within the month. In other words, the hint is misleading. There are 29 instances in the data of ships transiting on a Saturday in September in the 3PM hour, much more than 12. They just aren't on the same date (ordinal day within the month)
If you adjust to treat all the transits that passed at exactly the same time as a single bridge opening (regardless of direction of transit), and ignore the date and use the date/month instead, I believe the answer should be the 5PM hour on a Thursday in September for a total of 15 lifts. If you accept one of my premises but not the other, there are two more possible answers.
Solution attached.