The previous thread has fallen off the front page, feel free to use this for discussions on current problems
Rules: no spoilers, use the handy dandy spoiler preset to mark discussions as spoilers
The previous thread has fallen off the front page, feel free to use this for discussions on current problems
Rules: no spoilers, use the handy dandy spoiler preset to mark discussions as spoilers
Day 13, day 13 of shirking other responsibilities.
p1
Ok. So, I overthought this a little. Ultimately, this problem boils down to solving a system of 2 linear equations aka inverting a matrix.
Of course, anyone who has done undergraduate linear algebra knows to look to the determinant in case some shit goes down. For the general problem space, a zero determinant means that one equation is just a multiple of the other. A solution could still exist in this case. Consider:
a => x+1, y+1 b => x+2, y+2 x = 4, y = 4 (answer: 2 tokens)The following has no solution:
a => x+2, y+2 b => x+4, y+4 x = 3, y = 3I thought of all this, and instead of coding the solution, I just checked if any such cases were in my input. There weren’t, and I was home free.
p2
No real changes to the solution to p1 aside from the new targets. I wasn’t sure if 64 bit ints were big enough to fit the numbers so I changed my code to use big ints.
I’m looking at my code again and I’m pretty sure that was all unnecessary.
I liked day 13, a bit easy but in the right way.
Edit:
Spoilers
Although saying “minimum” was a bit evil when all of the systems had exactly 1 solution (not necessarily in ℕ^2), I wonder if it’s puzzle trickiness, anti-LLM (and unfortunate non comp-sci souls) trickiness or if the puzzle was maybe scaled down from a version where there are more solutions.
spoiler
Given the lack of edge cases, I feel the latter possibility is strong. I’m just glad it was easy!
13 commentary
Solved p1 by graph search before looking a bit closer on the examples and going, oh…
In pt2 I had some floating point weirdness when solving for keypress count, I was checking if the key presses where integers (can’t press button A five and half times after all) by checking if A = floor(A) and sometimes A would drop to the number below when floored, i.e. it was in reality (A-1).999999999999999999999999999999999999999999999. Whatever, I rounded it away but I did spend a stupid amount of time on it because it didn’t happen in the example set.