Advent of code

aoc2024/day1.nix

@@ -0,0 +1,18 @@
+let
+  lib = import <nixpkgs/lib>;
+
+  divWith = f: lib.sort (a: b: a < b) (map (x: f x) nums);
+  abs = x: if x < 0 then (-x) else x;
+  sum = x: lib.foldl (a: b: a + b) 0 x;
+
+  input = lib.removeSuffix "\n" (builtins.readFile ./input.txt);
+  nums = map (x: map (x: lib.toInt x) (lib.splitString "   " x)) (lib.splitString "\n" input);
+  left = divWith builtins.head;
+  right = divWith lib.last;
+  distances = lib.zipListsWith (a: b: abs (a - b)) left right;
+  similar = map (n: (builtins.mul n (lib.count (x: x == n) right))) left;
+in
+{
+  part1 = sum distances;
+  part2 = sum similar;
+}