advent-of-code-2021

My 2021 attempt at the https://adventofcode.com/ challenge.

Started writing the following on day 10, hence the lack of details :-)

Day 1: Sonar Sweep

Easy one

Day 2: Dive!

Easy one -= but decided it was worth my while to use map / reduce /filter

Day 3: Binary Diagnostic

Easy one.

Day 4: Giant Squid

Not a very smart implementation, but works. Part 2 is just part 1 with a few breaks removed to count till the end rather than stop at the first winning board

Day 5: Hydrothermal Venture

Easy one, once I stopped kidding myself there was some secret math to count intersections;

Day 6: Lanternfish

Part 1 was easy to achieve by tracking the cycle date per fish,

Part 2 is technically speaking the same than part 1, but the factorial blows the basic implementation out of the water, run out of memory, too many fish!!

I really struggled for a while, really thought there was some smart math at play.

In the end the trick was to stop tracking the cycle date per fish, and start tracking the number of fish at any date of the cycle.

Day 7: The Treachery of Whales

Part 1 I wasted a huge amount of time looking for smart math to solve it. Even looked into KD Trees!!!

In the end, wrote the basic code and got there :-)

Part 2 is not much more work after that, as long as you remember the triangle number formula

Day 8: Seven Segment Search

Part 1 is a slog but simple enough. Suspect there is a smart binary math method cleaner than all the switch statements, but beyond me I'm afraid

Part 2 took me a while. It's a bit like sudoku, figure our which order to eliminate possibilities

Day 9: Smoke Basin

First part is simple enough. Second part I haven't figure dout yet. Can solve th test case but not the full lot. I know hat I am looking for, I copied a solution from reddit, but can't see what it wrong with my solution. something to do with looking ahead...

maybe I could cheat and do 2 passes, the second one joining up any basins that I have not spotted were joined ... or recursion...

Day 10: Syntax Scoring

An easy one - but I have a cold and won't refactor my very basic implementation

Day 11: Dumbo Octopus

Weekend and ill, so not looked at it

Day 12: Passage Pathing

Weekend, and ill, so not looked at it

Day 13: Transparent Origami

Late doing it, but relatively easy. One smart(ish) thing I did was slice the array to reduce each iteration computation. Part 2 came naturally as I always log a lot before I can get my head around a problem