15
๐ฝ - 2024 DAY 14 SOLUTIONS - ๐ฝ
(programming.dev)
An unofficial home for the advent of code community on programming.dev!
Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.
Solution Threads
M | T | W | T | F | S | S |
---|---|---|---|---|---|---|
1 | ||||||
2 | 3 | 4 | 5 | 6 | 7 | 8 |
9 | 10 | 11 | 12 | 13 | 14 | 15 |
16 | 17 | 18 | 19 | 20 | 21 | 22 |
23 | 24 | 25 |
Icon base by Lorc under CC BY 3.0 with modifications to add a gradient
console.log('Hello World')
Haskell, alternative approach
The x and y coordinates of robots are independent. 101 and 103 are prime. So, the pattern of x coordinates will repeat every 101 ticks, and the pattern of y coordinates every 103 ticks.
For the first 101 ticks, take the histogram of x-coordinates and test it to see if it's roughly randomly scattered by performing a chi-squared test using a uniform distrobution as the basis. [That code's not given below, but it's a trivial transliteration of the formula on wikipedia, for instance.] In my case I found a massive peak at t=99.
Same for the first 103 ticks and y coordinates. Mine showed up at t=58.
You're then just looking for solutions of t = 101m + 99, t = 103n + 58 [in this case]. I've a library function, maybeCombineDiophantine, which computes the intersection of these things if any exist; again, this is basic wikipedia stuff.
I should add - it's perfectly possible to draw pictures which won't be spotted by this test, but in this case as it happens the distributions are exceedingly nonuniform at the critical point.
Very nice!
Very cool, taking a statistical approach to discern random noise from picture.
Thanks. It was the third thing I tried - began by looking for mostly-symmetrical, then asked myself "what does a christmas tree look like?" and wiring together some rudimentary heuristics. When those both failed (and I'd stopped for a coffee) the alternative struck me. It seems like a new avenue into the same diophantine fonisher that's pretty popular in these puzzles - quite an interesting one.
This day's puzzle is clearly begging for some inventive viaualisations.