adventofcode/2018/day04/problem

Advent of Code

--- Day 4: Repose Record ---

   You've sneaked into another supply closet - this time, it's across from the
   prototype suit manufacturing lab. You need to sneak inside and fix the
   issues with the suit, but there's a guard stationed outside the lab, so this
   is as close as you can safely get.

   As you search the closet for anything that might help, you discover that
   you're not the first person to want to sneak in. Covering the walls, someone
   has spent an hour starting every midnight for the past few months secretly
   observing this guard post! They've been writing down the ID of the one guard
   on duty that night - the Elves seem to have decided that one guard was
   enough for the overnight shift - as well as when they fall asleep or wake up
   while at their post (your puzzle input).

   For example, consider the following records, which have already been
   organized into chronological order:

 [1518-11-01 00:00] Guard #10 begins shift
 [1518-11-01 00:05] falls asleep
 [1518-11-01 00:25] wakes up
 [1518-11-01 00:30] falls asleep
 [1518-11-01 00:55] wakes up
 [1518-11-01 23:58] Guard #99 begins shift
 [1518-11-02 00:40] falls asleep
 [1518-11-02 00:50] wakes up
 [1518-11-03 00:05] Guard #10 begins shift
 [1518-11-03 00:24] falls asleep
 [1518-11-03 00:29] wakes up
 [1518-11-04 00:02] Guard #99 begins shift
 [1518-11-04 00:36] falls asleep
 [1518-11-04 00:46] wakes up
 [1518-11-05 00:03] Guard #99 begins shift
 [1518-11-05 00:45] falls asleep
 [1518-11-05 00:55] wakes up

   Timestamps are written using year-month-day hour:minute format. The guard
   falling asleep or waking up is always the one whose shift most recently
   started. Because all asleep/awake times are during the midnight hour (00:00
   - 00:59), only the minute portion (00 - 59) is relevant for those events.

   Visually, these records show that the guards are asleep at these times:

 Date   ID   Minute
             000000000011111111112222222222333333333344444444445555555555
             012345678901234567890123456789012345678901234567890123456789
 11-01  #10  .....####################.....#########################.....
 11-02  #99  ........................................##########..........
 11-03  #10  ........................#####...............................
 11-04  #99  ....................................##########..............
 11-05  #99  .............................................##########.....

   The columns are Date, which shows the month-day portion of the relevant day;
   ID, which shows the guard on duty that day; and Minute, which shows the
   minutes during which the guard was asleep within the midnight hour. (The
   Minute column's header shows the minute's ten's digit in the first row and
   the one's digit in the second row.) Awake is shown as ., and asleep is shown
   as #.

   Note that guards count as asleep on the minute they fall asleep, and they
   count as awake on the minute they wake up. For example, because Guard #10
   wakes up at 00:25 on 1518-11-01, minute 25 is marked as awake.

   If you can figure out the guard most likely to be asleep at a specific time,
   you might be able to trick that guard into working tonight so you can have
   the best chance of sneaking in. You have two strategies for choosing the
   best guard/minute combination.

   Strategy 1: Find the guard that has the most minutes asleep. What minute
   does that guard spend asleep the most?

   In the example above, Guard #10 spent the most minutes asleep, a total of 50
   minutes (20+25+5), while Guard #99 only slept for a total of 30 minutes
   (10+10+10). Guard #10 was asleep most during minute 24 (on two days, whereas
   any other minute the guard was asleep was only seen on one day).

   While this example listed the entries in chronological order, your entries
   are in the order you found them. You'll need to organize them before they
   can be analyzed.

   What is the ID of the guard you chose multiplied by the minute you chose?
   (In the above example, the answer would be 10 * 24 = 240.)

   Your puzzle answer was 102688.

--- Part Two ---

   Strategy 2: Of all guards, which guard is most frequently asleep on the same
   minute?

   In the example above, Guard #99 spent minute 45 asleep more than any other
   guard or minute - three times in total. (In all other cases, any guard spent
   any minute asleep at most twice.)

   What is the ID of the guard you chose multiplied by the minute you chose?
   (In the above example, the answer would be 99 * 45 = 4455.)

   Your puzzle answer was 56901.

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