Advent-of-Nix-2024/day2/default.nix

{ lib, utils, ... }:
with lib;
with builtins;
with utils;
let
  records = map (l: map toInt (splitWhitespace l)) (readLines ./input);
  getDeltas = r: zipListsWith sub (init r) (drop 1 r);
  isSafe = r:
    let deltas = getDeltas r;
    in (all (d: -3 <= d && d < 0) deltas) || (all (d: 3 >= d && d > 0) deltas);
  isSafeDampened = r: any isSafe (map (deleteAt r) (listRange r));
in {
  part1 = count isSafe records;
  part2 = count isSafeDampened records;
}