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And we're off!
I wonder if I got a bit too clever by half in this solution, as I've been looking over older solutions and can't even remember solving them. But that's how it goes I guess.
Puzzle rating: 3/5
Score: 2
A "standard" Perlish solution (well, *my* kind of Perl, anyway): a dispatch table for the else/if "switch" construct, and a compact hash containing the state of the two solutions.
Puzzle rating: 3/5
Score: 2
I was honestly surprised that the canonical solution to this wasn't some esoteric bit-twiddling trick that reduces it to a one-liner.
In part 2, the naive solution is to loop through each "column" to determine which values to count so as to determine whether they are most frequent or not. I used an index for each "set" to keep track of the values already assigned to that set.
Puzzle rating: 3/5
Score: 2
Fairly straight-forward, although part 2 threw me for a loop. I didn't find a good way to determine the exit condition.
Puzzle rating: 4/5
Score: 2
Finally ok with my solution.
The first attempt got the job done, but was super-scruffy. I realized after I'd finished that I could treat the direction as unit vectors and work from there, so I re-wrote my solution, but only in as so far as to use the direction as a "selector" to chose which subroutine to call to "paint" the map.
After adding that to the repo, I finally remembered what I'd decided before the rewrite - to use the value of the vector in the paint routine itself.
Note that just using `atan2` blindly to determine the direction will point the Y axis incorrectly. It's probably only an issue if you're printing the results, but I found that very helpful in debugging.
If anything good can be said about this method is that I eliminated a lot of weirdness along the way. It wasn't all wasted effort.
Puzzle rating: 3/5
Score: 2
I got off on a bad start with this puzzle, because it worked perfectly for the test input but failed for my puzzle input. I whinged about it on IRC, mentioning I had a very old fish (41 days!). Turns out that was a mispaste and fixing that gave me the correct solution.
I got the answer to the second part 40 seconds later.
Puzzle rating: 4/5, just because my solution was so smooooth
Score: 2
A quite fun one, and the first this year I managed to solve within 1hr of release. This might be TMI but I usually perform my morning ablutions and brew a pot of coffee before starting on a puzzle.
Thinking about this led me to try the average (mean) of the values as the natural solution, but that gave incorrect values. So I just checked the fuel consumption for each and every possible end point, selecting the minimum value. This went plenty fast, as did part 2 once I didn't actually step through each distance calculating fuel as I went (hint: google "Gauss sum 100").
When I had both solutions, I checked the various IRC chats and subreddits and discovered a raging debate on whether taking the median for part 1 and the average for part 2 always gave the correct result for every input. For me they did, so I just restricted by search space to the span of these values, plus a few extra integers for safety. This shaved a couple more milliseconds off the run time.
Puzzle rating: 4/5, I like grade school math
Score: 2
Today was a tough one - not the problem, per se, but commitments that made it hard to me to get to a solution that I was happy with.
In the end I just went for brute-forcing every possible permutation, which is 7! or 5,040. The solution takes around 2s to run on my VPS.
Puzzle rating: 3/5, bit fiddly
Score: 2
This was a straight-forward problem.
I'm a bit surprised my BFS solution worked first time.
Puzzle rating: 3/5
Score: 2
Not the most elegant solution but it gets the job done.
Puzzle rating: 3/5
Score: 2
Nice and easy, got 2 stars within one hour of downloading the input.
I don't think my handling of some flags (`$has_changed`, `$has_synced`) is the most elegant. I'm pretty sure I'm doing an extra scan of the entire map every step to ensure everything has settled down. But I get a result within 1s (*just*) so let's do some weekend chores instead.
I suspect tomorrow will be... more challenging.
Puzzle rating: 3/5
Score: 2
As usual, a breather after the weekend.
I was tearing my hair out, running spot checks on my code, before I realized I had coded my output incorrectly.
The rest of my issues was making it read the right way up...
"Best" result so far, around rank 6,500 for part 1...
Puzzle rating: 3/5
Score: 2
A tough but fun problem.
Part 1 only for now.
Puzzle rating: 4/5
Score: 2
I think I finally figured out <strike>A\*</strike>Dijkstra's. With the help of a lot of cribbing from previous solutions (like 2018 day 22).
I've only included part 2 because I can't be bothered bounding the box for part 1 so it doesn't choose a cheaper solution outside those limits.
Puzzle rating: 4/5
Score: 2
Many people went "BERR" when they saw this: Binary Encoded Register Rodeo!
I had a lot of problems with this, mostly because I managed to get the correct solution for part one a bit by accident, which didn't help solving part 2.
After a day of tearing my hair trying to pass data between recursion levels I managed to solve it.
Puzzle rating: 4/5 - tough, but fair
Score: 2
Suspiciously easy.
This year's last weekend is coming up.
Brace yourselves.
Puzzle rating: 3/5
Score: 2
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Updated on Friday, 2021-12-17
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