121 lines
5.1 KiB
Plaintext
121 lines
5.1 KiB
Plaintext
Advent of Code
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--- Day 4: Repose Record ---
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You've sneaked into another supply closet - this time, it's across from the
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prototype suit manufacturing lab. You need to sneak inside and fix the
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issues with the suit, but there's a guard stationed outside the lab, so this
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is as close as you can safely get.
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As you search the closet for anything that might help, you discover that
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you're not the first person to want to sneak in. Covering the walls, someone
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has spent an hour starting every midnight for the past few months secretly
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observing this guard post! They've been writing down the ID of the one guard
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on duty that night - the Elves seem to have decided that one guard was
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enough for the overnight shift - as well as when they fall asleep or wake up
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while at their post (your puzzle input).
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For example, consider the following records, which have already been
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organized into chronological order:
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[1518-11-01 00:00] Guard #10 begins shift
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[1518-11-01 00:05] falls asleep
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[1518-11-01 00:25] wakes up
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[1518-11-01 00:30] falls asleep
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[1518-11-01 00:55] wakes up
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[1518-11-01 23:58] Guard #99 begins shift
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[1518-11-02 00:40] falls asleep
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[1518-11-02 00:50] wakes up
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[1518-11-03 00:05] Guard #10 begins shift
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[1518-11-03 00:24] falls asleep
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[1518-11-03 00:29] wakes up
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[1518-11-04 00:02] Guard #99 begins shift
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[1518-11-04 00:36] falls asleep
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[1518-11-04 00:46] wakes up
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[1518-11-05 00:03] Guard #99 begins shift
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[1518-11-05 00:45] falls asleep
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[1518-11-05 00:55] wakes up
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Timestamps are written using year-month-day hour:minute format. The guard
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falling asleep or waking up is always the one whose shift most recently
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started. Because all asleep/awake times are during the midnight hour (00:00
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- 00:59), only the minute portion (00 - 59) is relevant for those events.
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Visually, these records show that the guards are asleep at these times:
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Date ID Minute
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000000000011111111112222222222333333333344444444445555555555
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012345678901234567890123456789012345678901234567890123456789
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11-01 #10 .....####################.....#########################.....
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11-02 #99 ........................................##########..........
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11-03 #10 ........................#####...............................
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11-04 #99 ....................................##########..............
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11-05 #99 .............................................##########.....
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The columns are Date, which shows the month-day portion of the relevant day;
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ID, which shows the guard on duty that day; and Minute, which shows the
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minutes during which the guard was asleep within the midnight hour. (The
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Minute column's header shows the minute's ten's digit in the first row and
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the one's digit in the second row.) Awake is shown as ., and asleep is shown
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as #.
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Note that guards count as asleep on the minute they fall asleep, and they
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count as awake on the minute they wake up. For example, because Guard #10
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wakes up at 00:25 on 1518-11-01, minute 25 is marked as awake.
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If you can figure out the guard most likely to be asleep at a specific time,
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you might be able to trick that guard into working tonight so you can have
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the best chance of sneaking in. You have two strategies for choosing the
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best guard/minute combination.
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Strategy 1: Find the guard that has the most minutes asleep. What minute
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does that guard spend asleep the most?
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In the example above, Guard #10 spent the most minutes asleep, a total of 50
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minutes (20+25+5), while Guard #99 only slept for a total of 30 minutes
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(10+10+10). Guard #10 was asleep most during minute 24 (on two days, whereas
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any other minute the guard was asleep was only seen on one day).
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While this example listed the entries in chronological order, your entries
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are in the order you found them. You'll need to organize them before they
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can be analyzed.
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What is the ID of the guard you chose multiplied by the minute you chose?
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(In the above example, the answer would be 10 * 24 = 240.)
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Your puzzle answer was 102688.
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--- Part Two ---
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Strategy 2: Of all guards, which guard is most frequently asleep on the same
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minute?
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In the example above, Guard #99 spent minute 45 asleep more than any other
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guard or minute - three times in total. (In all other cases, any guard spent
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any minute asleep at most twice.)
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What is the ID of the guard you chose multiplied by the minute you chose?
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(In the above example, the answer would be 99 * 45 = 4455.)
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Your puzzle answer was 56901.
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References
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Visible links
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. https://adventofcode.com/
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. https://adventofcode.com/2018/about
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. https://adventofcode.com/2018/events
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. https://adventofcode.com/2018/settings
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. https://adventofcode.com/2018/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2018/support
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018/support
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. https://adventofcode.com/2018/sponsors
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. https://adventofcode.com/2018/leaderboard
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. https://adventofcode.com/2018/stats
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. https://adventofcode.com/2018/sponsors
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018/day/4/input
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