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AdventOfCode23

Advent of Code 2023. Solutions in Julia.

Lessons from each day

(an idea copied from Fergus's Advent of Code 2023)

  • 01: Can match regular expressions.
  • 02: A dictionary, Dict, was helpful.
  • 03: checkbounds to check array bounds. Can use ∉ which is nice.
  • 04: CSV reader has a boolean option ignorerepeated.
  • 05: It can be annoying doing part A before part B - ha ha. Need to get better at using the "!" convention in function names that mutate their arguments. This one was tricky!
  • 06: Shameless brute force solution as an antidote to 05. Used replace to get rid of the spaces.
  • 07: Sorting.
  • 08: Mapping file didn't start at AAA. lcm - yay! And falses.
  • 09: pushfirst!
  • 10: Part A bit more awkward than anticipated. Part B forgot to replace the starting point when looking for enclosed spaces.
  • 11: reverse. count can be used to count numbers true's in an array.
  • 12: Strings are immutable. Who knew? Also Threads.@threads (but don't need this with an efficient code!). Memoization. Lots to learn with this one!
  • 13: transpose.
  • 14: Easy to be out of phase by ±1 if not careful.
  • 15: Comprehensions and generators.
  • 16: count syntax for counting elements in an array that satisfy some condition.
  • 17: Learn linear programming! JuMP. Tried lazy constraints which was an interesting exercise. However, redefining the nodes to have different directional states was a better approach and reduced the number of additional constraints.
  • 18: Shoelace formula - wish I'd known about this before! "Obvious" result that makes the computation much easier. parse can take base argument.
  • 19: eval(Meta.parse(expression)). Haven't done part B yet.
  • 20: Use arrays to "allow" mutable elements in dictionary.
  • 21: I wonder what part B will bring. Ug - this one is tricky! Haven't done part B yet.
  • 22: Intersections.
  • 23: Part A took longer than expected given that code was recycled. Part B - need to eliminate sub-tours.
  • 24: Overkill for part A but thought I'd investigate how to solve a set of linear equations in Julia. SciML/LinearSolve.jl. Also for part B, NonlinearSolve.jl, even though I didn't end up using this.