191 lines
6.0 KiB
Markdown
191 lines
6.0 KiB
Markdown
|
## \-\-- Day 25: Code Chronicle \-\--
|
||
|
|
|
||
|
|
Out of ideas and time, The Historians agree that they should go back to
|
||
|
|
check the *Chief Historian\'s office* one last time, just in case he
|
||
|
|
went back there without you noticing.
|
||
|
|
|
||
|
|
When you get there, you are surprised to discover that the door to his
|
||
|
|
office is *locked*! You can hear someone inside, but knocking
|
||
|
|
[yields]{title="function knock() {
|
||
|
|
yield no_response;
|
||
|
|
}"} no response. The locks on this floor are all fancy, expensive,
|
||
|
|
virtual versions of [five-pin tumbler
|
||
|
|
locks](https://en.wikipedia.org/wiki/Pin_tumbler_lock),
|
||
|
|
so you contact North Pole security to see if they can help open the
|
||
|
|
door.
|
||
|
|
|
||
|
|
Unfortunately, they\'ve lost track of which locks are installed and
|
||
|
|
which keys go with them, so the best they can do is send over
|
||
|
|
*schematics of every lock and every key* for the floor you\'re on (your
|
||
|
|
puzzle input).
|
||
|
|
|
||
|
|
The schematics are in a cryptic file format, but they do contain
|
||
|
|
manufacturer information, so you look up their support number.
|
||
|
|
|
||
|
|
\"Our Virtual Five-Pin Tumbler product? That\'s our most expensive
|
||
|
|
model! *Way* more secure than\--\" You explain that you need to open a
|
||
|
|
door and don\'t have a lot of time.
|
||
|
|
|
||
|
|
\"Well, you can\'t know whether a key opens a lock without actually
|
||
|
|
trying the key in the lock (due to quantum hidden variables), but you
|
||
|
|
*can* rule out some of the key/lock combinations.\"
|
||
|
|
|
||
|
|
\"The virtual system is complicated, but part of it really is a crude
|
||
|
|
simulation of a five-pin tumbler lock, mostly for marketing reasons. If
|
||
|
|
you look at the schematics, you can figure out whether a key could
|
||
|
|
possibly fit in a lock.\"
|
||
|
|
|
||
|
|
He transmits you some example schematics:
|
||
|
|
|
||
|
|
#####
|
||
|
|
.####
|
||
|
|
.####
|
||
|
|
.####
|
||
|
|
.#.#.
|
||
|
|
.#...
|
||
|
|
.....
|
||
|
|
|
||
|
|
#####
|
||
|
|
##.##
|
||
|
|
.#.##
|
||
|
|
...##
|
||
|
|
...#.
|
||
|
|
...#.
|
||
|
|
.....
|
||
|
|
|
||
|
|
.....
|
||
|
|
#....
|
||
|
|
#....
|
||
|
|
#...#
|
||
|
|
#.#.#
|
||
|
|
#.###
|
||
|
|
#####
|
||
|
|
|
||
|
|
.....
|
||
|
|
.....
|
||
|
|
#.#..
|
||
|
|
###..
|
||
|
|
###.#
|
||
|
|
###.#
|
||
|
|
#####
|
||
|
|
|
||
|
|
.....
|
||
|
|
.....
|
||
|
|
.....
|
||
|
|
#....
|
||
|
|
#.#..
|
||
|
|
#.#.#
|
||
|
|
#####
|
||
|
|
|
||
|
|
\"The locks are schematics that have the top row filled (`#`) and the
|
||
|
|
bottom row empty (`.`); the keys have the top row empty and the bottom
|
||
|
|
row filled. If you look closely, you\'ll see that each schematic is
|
||
|
|
actually a set of columns of various heights, either extending downward
|
||
|
|
from the top (for locks) or upward from the bottom (for keys).\"
|
||
|
|
|
||
|
|
\"For locks, those are the pins themselves; you can convert the pins in
|
||
|
|
schematics to a list of heights, one per column. For keys, the columns
|
||
|
|
make up the shape of the key where it aligns with pins; those can also
|
||
|
|
be converted to a list of heights.\"
|
||
|
|
|
||
|
|
\"So, you could say the first lock has pin heights `0,5,3,4,3`:\"
|
||
|
|
|
||
|
|
#####
|
||
|
|
.####
|
||
|
|
.####
|
||
|
|
.####
|
||
|
|
.#.#.
|
||
|
|
.#...
|
||
|
|
.....
|
||
|
|
|
||
|
|
\"Or, that the first key has heights `5,0,2,1,3`:\"
|
||
|
|
|
||
|
|
.....
|
||
|
|
#....
|
||
|
|
#....
|
||
|
|
#...#
|
||
|
|
#.#.#
|
||
|
|
#.###
|
||
|
|
#####
|
||
|
|
|
||
|
|
\"These seem like they should fit together; in the first four columns,
|
||
|
|
the pins and key don\'t overlap. However, this key *cannot* be for this
|
||
|
|
lock: in the rightmost column, the lock\'s pin overlaps with the key,
|
||
|
|
which you know because in that column the sum of the lock height and key
|
||
|
|
height is more than the available space.\"
|
||
|
|
|
||
|
|
\"So anyway, you can narrow down the keys you\'d need to try by just
|
||
|
|
testing each key with each lock, which means you would have to check\...
|
||
|
|
wait, you have *how* many locks? But the only installation *that* size
|
||
|
|
is at the North\--\" You disconnect the call.
|
||
|
|
|
||
|
|
In this example, converting both locks to pin heights produces:
|
||
|
|
|
||
|
|
0,5,3,4,3
|
||
|
|
1,2,0,5,3
|
||
|
|
|
||
|
|
Converting all three keys to heights produces:
|
||
|
|
|
||
|
|
5,0,2,1,3
|
||
|
|
4,3,4,0,2
|
||
|
|
3,0,2,0,1
|
||
|
|
|
||
|
|
Then, you can try every key with every lock:
|
||
|
|
|
||
|
|
- Lock `0,5,3,4,3` and key `5,0,2,1,3`: *overlap* in the last column.
|
||
|
|
- Lock `0,5,3,4,3` and key `4,3,4,0,2`: *overlap* in the second
|
||
|
|
column.
|
||
|
|
- Lock `0,5,3,4,3` and key `3,0,2,0,1`: all columns *fit*!
|
||
|
|
- Lock `1,2,0,5,3` and key `5,0,2,1,3`: *overlap* in the first column.
|
||
|
|
- Lock `1,2,0,5,3` and key `4,3,4,0,2`: all columns *fit*!
|
||
|
|
- Lock `1,2,0,5,3` and key `3,0,2,0,1`: all columns *fit*!
|
||
|
|
|
||
|
|
So, in this example, the number of unique lock/key pairs that fit
|
||
|
|
together without overlapping in any column is `3`.
|
||
|
|
|
||
|
|
Analyze your lock and key schematics. *How many unique lock/key pairs
|
||
|
|
fit together without overlapping in any column?*
|
||
|
|
|
||
|
|
Your puzzle answer was `3395`.
|
||
|
|
|
||
|
|
The first half of this puzzle is complete! It provides one gold star: \*
|
||
|
|
|
||
|
|
## \-\-- Part Two \-\-- {#part2}
|
||
|
|
|
||
|
|
You and The Historians crowd into the office, startling the Chief
|
||
|
|
Historian awake! The Historians all take turns looking confused until
|
||
|
|
one asks where he\'s been for the last few months.
|
||
|
|
|
||
|
|
\"I\'ve been right here, working on this high-priority request from
|
||
|
|
Santa! I think the only time I even stepped away was about a month ago
|
||
|
|
when I went to grab a cup of coffee\...\"
|
||
|
|
|
||
|
|
Just then, the Chief notices the time. \"Oh no! I\'m going to be late! I
|
||
|
|
must have fallen asleep trying to put the finishing touches on this
|
||
|
|
*chronicle* Santa requested, but now I don\'t have enough time to go
|
||
|
|
visit the last 50 places on my list and complete the chronicle before
|
||
|
|
Santa leaves! He said he needed it before tonight\'s sleigh launch.\"
|
||
|
|
|
||
|
|
One of The Historians holds up the list they\'ve been using this whole
|
||
|
|
time to keep track of where they\'ve been searching. Next to each place
|
||
|
|
you all visited, they checked off that place with a *star*. Other
|
||
|
|
Historians hold up their own notes they took on the journey; as The
|
||
|
|
Historians, how could they resist writing everything down while visiting
|
||
|
|
all those historically significant places?
|
||
|
|
|
||
|
|
The Chief\'s eyes get wide. \"With all this, we might just have enough
|
||
|
|
time to finish the chronicle! Santa said he wanted it wrapped up with a
|
||
|
|
bow, so I\'ll call down to the wrapping department and\... hey, could
|
||
|
|
*you* bring it up to Santa? I\'ll need to be in my seat to watch the
|
||
|
|
sleigh launch by then.\"
|
||
|
|
|
||
|
|
You nod, and The Historians quickly work to collect their notes into the
|
||
|
|
final set of pages for the chronicle.
|
||
|
|
|
||
|
|
You don\'t have enough stars to finish the chronicle, though. You need
|
||
|
|
13 more.
|
||
|
|
|
||
|
|
Although it hasn\'t changed, you can still [get your puzzle
|
||
|
|
input](25/input).
|
||
|
|
|