2025 Day 11 Complete!

2025/day11/problem

@@ -0,0 +1,141 @@
+[1]Advent of Code
+   br0xen [7](AoC++) 22*
+
+--- Day 11: Reactor ---
+
+   You hear some loud beeping coming from a hatch in the floor of the
+   factory, so you decide to check it out. Inside, you find several large
+   electrical conduits and a ladder.
+
+   Climbing down the ladder, you discover the source of the beeping: a large,
+   toroidal reactor which powers the factory above. Some Elves here are
+   hurriedly running between the reactor and a nearby server rack, apparently
+   trying to fix something.
+
+   One of the Elves notices you and rushes over. "It's a good thing you're
+   here! We just installed a new server rack, but we aren't having any luck
+   getting the reactor to communicate with it!" You glance around the room
+   and see a tangle of cables and devices running from the server rack to the
+   reactor. She rushes off, returning a moment later with a list of the
+   devices and their outputs (your puzzle input).
+
+   For example:
+
+ aaa: you hhh
+ you: bbb ccc
+ bbb: ddd eee
+ ccc: ddd eee fff
+ ddd: ggg
+ eee: out
+ fff: out
+ ggg: out
+ hhh: ccc fff iii
+ iii: out
+
+   Each line gives the name of a device followed by a list of the devices to
+   which its outputs are attached. So, bbb: ddd eee means that device bbb has
+   two outputs, one leading to device ddd and the other leading to device
+   eee.
+
+   The Elves are pretty sure that the issue isn't due to any specific device,
+   but rather that the issue is triggered by data following some specific
+   path through the devices. Data only ever flows from a device through its
+   outputs; it can't flow backwards.
+
+   After dividing up the work, the Elves would like you to focus on the
+   devices starting with the one next to you (an Elf hastily attaches a label
+   which just says you) and ending with the main output to the reactor (which
+   is the device with the label out).
+
+   To help the Elves figure out which path is causing the issue, they need
+   you to find every path from you to out.
+
+   In this example, these are all of the paths from you to out:
+
+     • Data could take the connection from you to bbb, then from bbb to ddd,
+       then from ddd to ggg, then from ggg to out.
+     • Data could take the connection to bbb, then to eee, then to out.
+     • Data could go to ccc, then ddd, then ggg, then out.
+     • Data could go to ccc, then eee, then out.
+     • Data could go to ccc, then fff, then out.
+
+   In total, there are 5 different paths leading from you to out.
+
+   How many different paths lead from you to out?
+
+   Your puzzle answer was 585.
+
+--- Part Two ---
+
+   Thanks in part to your analysis, the Elves have figured out a little bit
+   about the issue. They now know that the problematic data path passes
+   through both dac (a [16]digital-to-analog converter) and fft (a device
+   which performs a [17]fast Fourier transform).
+
+   They're still not sure which specific path is the problem, and so they now
+   need you to find every path from svr (the server rack) to out. However,
+   the paths you find must all also visit both dac and fft (in any order).
+
+   For example:
+
+ svr: aaa bbb
+ aaa: fft
+ fft: ccc
+ bbb: tty
+ tty: ccc
+ ccc: ddd eee
+ ddd: hub
+ hub: fff
+ eee: dac
+ dac: fff
+ fff: ggg hhh
+ ggg: out
+ hhh: out
+
+   This new list of devices contains many paths from svr to out:
+
+ svr,aaa,fft,ccc,ddd,hub,fff,ggg,out
+ svr,aaa,fft,ccc,ddd,hub,fff,hhh,out
+ svr,aaa,fft,ccc,eee,dac,fff,ggg,out
+ svr,aaa,fft,ccc,eee,dac,fff,hhh,out
+ svr,bbb,tty,ccc,ddd,hub,fff,ggg,out
+ svr,bbb,tty,ccc,ddd,hub,fff,hhh,out
+ svr,bbb,tty,ccc,eee,dac,fff,ggg,out
+ svr,bbb,tty,ccc,eee,dac,fff,hhh,out
+
+   However, only 2 paths from svr to out visit both dac and fft.
+
+   Find all of the paths that lead from svr to out. How many of those paths
+   visit both dac and fft?
+
+   Your puzzle answer was 349322478796032.
+
+   Both parts of this puzzle are complete! They provide two gold stars: **
+
+   At this point, you should [18]return to your Advent calendar and try
+   another puzzle.
+
+   If you still want to see it, you can [19]get your puzzle input.
+
+References
+
+   Visible links
+   1. https://adventofcode.com/
+   2. https://adventofcode.com/2025/about
+   3. https://adventofcode.com/2025/events
+   4. https://adventofcode.com/2025/shop
+   5. https://adventofcode.com/2025/settings
+   6. https://adventofcode.com/2025/auth/logout
+   7. Advent of Code Supporter
+	https://adventofcode.com/2025/support
+   8. https://adventofcode.com/2025
+   9. https://adventofcode.com/2025
+  10. https://adventofcode.com/2025/support
+  11. https://adventofcode.com/2025/sponsors
+  12. https://adventofcode.com/2025/leaderboard/private
+  13. https://adventofcode.com/2025/stats
+  14. https://adventofcode.com/2025/sponsors
+  16. https://en.wikipedia.org/wiki/Digital-to-analog_converter
+  17. https://en.wikipedia.org/wiki/Fast_Fourier_transform
+  18. https://adventofcode.com/2025
+  19. https://adventofcode.com/2025/day/11/input