2024 day 15 part 1 in nix

2024/15/example.txt

@@ -0,0 +1,21 @@
+##########
+#..O..O.O#
+#......O.#
+#.OO..O.O#
+#..O@..O.#
+#O#..O...#
+#O..O..O.#
+#.OO.O.OO#
+#....O...#
+##########
+
+<vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
+vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
+><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
+<<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
+^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
+^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
+>^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
+<><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
+^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
+v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^

2024/15/example2.txt

@@ -0,0 +1,10 @@
+########
+#..O.O.#
+##@.O..#
+#...O..#
+#.#.O..#
+#...O..#
+#......#
+########
+
+<^^>>>vv<v>>v<<

2024/15/solution.nix

@@ -0,0 +1,97 @@
+{lib, ...}: input: rec {
+  inherit lib;
+  inherit (lib) splitString mod;
+  inherit (lib.lists) findFirstIndex imap0;
+  inherit (lib.strings) stringToCharacters;
+  inherit (builtins) elemAt concatStringsSep length elem filter foldl' concatLists;
+
+  index = i: list: elemAt list i;
+  index2d = {x, y}: m: m |> index y |> index x;
+
+  init = let
+    parts = splitString "\n\n" input;
+    chart = elemAt parts 0 |> splitString "\n" |> map stringToCharacters;
+    # ins = elemAt parts 1 |> stringToCharacters |> filter (char: elem char (stringToCharacters "^><v"));
+    ins = elemAt parts 1 |> splitString "\n" |> map stringToCharacters;
+    width = (elemAt chart 0 |> length) + 1;
+    startIndex = elemAt parts 0 |> stringToCharacters |> findFirstIndex (char: char == "@") null;
+  in {
+    inherit chart ins;
+    pos = {
+      x = mod startIndex width;
+      y = startIndex / width;
+    };
+  }
+  ;
+
+  addVec = a: b: {x = a.x + b.x; y = a.y + b.y;};
+
+  objects = {
+    wall = "#";
+    moveable = "O";
+    empty = ".";
+  };
+
+  replace2d = {x, y}: updated: chart: let
+    newRow = chart |> index y |> replace x updated;
+  in
+    replace y newRow chart;
+
+  replace = i: updated: list: 
+  let before = lib.sublist 0 i list;
+    after = lib.sublist (i + 1) (builtins.length list - i) list;
+  in
+    if i < 0 || i > builtins.length list then list else
+    before ++ [updated] ++ after;
+
+  strToDir = strDir: {
+    x = if strDir == "<" then -1 else if strDir == ">" then 1 else 0;
+    y = if strDir == "^" then -1 else if strDir == "v" then 1 else 0;
+  };
+  
+  move = {chart, pos, ...}: dir: let
+    nextPos = addVec pos dir;
+    atPos = chart |> index2d pos;
+    moved = move {inherit chart; pos = nextPos;} dir;
+  in if atPos == objects.wall
+  then {
+    inherit chart pos;
+    moved = false;
+  } else if atPos == objects.empty
+  then {
+    inherit chart pos;
+    moved = true;
+  } else if !moved.moved
+  then {inherit chart pos; moved = false;}
+  else {
+    moved = true;
+    pos = nextPos;
+    chart = moved.chart |> replace2d pos objects.empty |> replace2d nextPos atPos;
+  };
+
+  chartToStr = chart: chart |> (map (concatStringsSep "")) |> concatStringsSep "\n";
+
+  applyIns = foldl' (c: ins: let
+    dir = strToDir ins;
+  in move c dir);
+
+  applyInsList = foldl' (chart: ins:
+    # evaluate each line of instructions one at a time, to avoid stack overflow.
+    let res = applyIns chart ins; in builtins.deepSeq res
+    (res)
+  );
+
+  result = applyInsList init init.ins;
+
+  getScore = chart: chart
+    |> imap0 (y: row: row
+      |> imap0 (x: obj:
+        if obj == objects.moveable then x + y * 100 else 0
+      )
+    )
+    |> concatLists
+    |> foldl' builtins.add 0
+  ;
+
+  part1result = getScore result.chart;
+}

2024/flake.lock

@@ -3,8 +3,8 @@
     "aoc-inputs": {
       "flake": false,
       "locked": {
-        "lastModified": 1734173652,
-        "narHash": "sha256-jXnmQLoXNcaqYY/uupC8f8JQ27zdwSVBmxAnIxlennk=",
+        "lastModified": 1734266579,
+        "narHash": "sha256-fhPoaCWITp2KZtdxm+D9e6GiWf+c3/RGJeiq03/ynfY=",
         "path": "/tmp/aoc-inputs",
         "type": "path"
       },

2024/flake.nix

@@ -25,15 +25,17 @@
     inherit (pkgs) lib;
 
 
-  in (lib.range 1 14
+  in (lib.range 1 15
   |> map (i: let id = lib.fixedWidthNumber 2 i; in {
     name = "day-${id}";
     value = let
       solution = import ./${id}/solution.nix pkgs;
       example = (pkgs.lib.readFile ./${id}/example.txt);
+      example2 = (pkgs.lib.readFile ./${id}/example2.txt);
       input = (pkgs.lib.readFile "${aoc-inputs}/${id}");
     in {
       example = solution example;
+      example2 = solution example2;
       real = solution input;
       test = tix.run [
         ./${id}/solution.test.nix