2024 day 18 part 1
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25
2024/18/example.txt
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25
2024/18/example.txt
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5,4
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4,2
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4,5
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3,0
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2,1
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6,3
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2,4
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1,5
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0,6
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3,3
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2,6
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5,1
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1,2
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5,5
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2,5
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6,5
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1,4
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0,4
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6,4
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1,1
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6,1
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1,0
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0,5
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1,6
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2,0
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52
2024/18/solution.nix
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52
2024/18/solution.nix
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{lib, input ? "", my-lib, ...}@pkgs: rec {
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inherit pkgs;
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inherit lib;
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inherit (builtins) elemAt genList elem concatStringsSep;
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inherit (lib) splitString;
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inherit (lib.strings) toIntBase10;
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init = input: input |> lib.trim
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|> splitString "\n"
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|> map (line: let c = splitString "," line; in {
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x = elemAt c 0 |> toIntBase10;
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y = elemAt c 1 |> toIntBase10;
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})
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;
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genChart = size: coords: genList (y: genList (x:
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if x == 0 && y == 0 then "S" else
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if x == size - 1 && y == size - 1 then "E" else
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if elem {inherit x y;} coords then "#" else "."
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) size) size;
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chartToStr = chart: chart |> (map (concatStringsSep "")) |> concatStringsSep "\n";
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mkSolution = {size, bytes, input}: rec {
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inherit size bytes input;
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walls = lib.sublist 0 bytes (init input);
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chart = genChart size walls;
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part1result = dijkstra.toGoal.steps;
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dijkstra = my-lib.dijkstra {
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pos = {x = 0; y = 0;};
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goal = {x = size - 1; y = size - 1;};
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chart = chart;
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width = size;
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height = size;
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};
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};
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example = mkSolution {
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size = 7;
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bytes = 12;
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input = lib.readFile ./example.txt;
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};
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real = mkSolution {
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size = 71;
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bytes = 1024;
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input = input;
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};
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# not 272, too high
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}
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@ -3,8 +3,8 @@
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"aoc-inputs": {
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"flake": false,
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"locked": {
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"lastModified": 1734334657,
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"narHash": "sha256-NjsEC/6Mu+i94YPgK4yN0Y5TxhlWwXK5Ev2UzIkfGZo=",
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"lastModified": 1734543082,
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"narHash": "sha256-hU8vRkPOKfQqp34Ffx4INiz3l6HdwGcbfyHgqO4qheM=",
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"path": "/tmp/aoc-inputs",
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"type": "path"
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},
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@ -29,12 +29,16 @@
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|> map (i: let id = lib.fixedWidthNumber 2 i; in {
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name = "day-${id}";
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value = let
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solution = import ./${id}/solution.nix pkgs;
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solution = import ./${id}/solution.nix ( pkgs // {
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my-lib = import ./lib/. pkgs;
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inherit input;
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} );
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example = (pkgs.lib.readFile ./${id}/example.txt);
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example2 = (pkgs.lib.readFile ./${id}/example2.txt);
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example3 = (pkgs.lib.readFile ./${id}/example3.txt);
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input = (pkgs.lib.readFile "${aoc-inputs}/${id}");
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in {
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inherit solution;
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example = solution example;
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example2 = solution example2;
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example3 = solution example3;
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3
2024/lib/default.nix
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3
2024/lib/default.nix
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pkgs: {
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dijkstra = import ./dijkstra.nix pkgs;
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}
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212
2024/lib/dijkstra.nix
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212
2024/lib/dijkstra.nix
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{lib, pkgs, ...}: {pos, goal, chart, width, height}@init: rec {
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inherit lib;
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inherit (lib) splitString mod range;
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inherit (lib.lists) findFirstIndex imap0;
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inherit (lib.strings) stringToCharacters;
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inherit (builtins) elemAt concatStringsSep length elem filter foldl' concatLists floor deepSeq listToAttrs attrValues attrNames mapAttrs hasAttr sort genList;
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index = i: list: if isNull list || i < 0 || i >= length list then null else elemAt list i;
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index2d = {x, y}: m: m |> index y |> index x;
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chartToStr = chart: chart |> (map (concatStringsSep "")) |> concatStringsSep "\n";
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rotate' = {x, y}: {y = -x; x = y;};
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rotate = {x, y}: {y = x; x = -y;};
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addVec = a: b: {x = a.x or 0 + b.x or 0; y = a.y or 0 + b.y or 0;};
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multVec = a: m: {x = a.x or 0 * m; y = a.y or 0 * m;};
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dirs = {
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north = {x = 0; y = -1;};
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east = {x = 1; y = 0;};
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south = {x = 0; y = 1;};
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west = {x = -1; y = 0;};
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};
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search = {
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pos,
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dir,
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score ? 0,
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}: let
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fwd = addVec pos dir;
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in
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if
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elem (index2d fwd init.chart) [null "#"]
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then {pos = null; dist = null;}
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else
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if (isCorner fwd || fwd == init.goal || fwd == init.pos)
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then {
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pos = (key fwd);
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dist = score + 1;
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}
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else
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search {pos = fwd; inherit dir; score = score + 1;}
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;
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isCorner = pos: index2d pos init.chart == "." &&
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(dirs
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|> mapAttrs (name: dir: let n = addVec pos dir; in index2d n init.chart == ".")
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|> ({north, east, south, west}:
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north && east || east && south || south && west || west && north))
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;
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key = {x, y}: "${toString (y + 1)},${toString (x + 1)}";
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corners = range 0 (init.width - 1) |> map (x:
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range 0 (init.height - 1) |> map (y: {inherit x y;})
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)
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|> concatLists
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|> filter isCorner
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|> (nodes: nodes ++ [init.pos init.goal])
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|> map (pos: {
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name = key pos;
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value = ({
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north = search {inherit pos; dir = dirs.north;};
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east = search {inherit pos; dir = dirs.east;};
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south = search {inherit pos; dir = dirs.south;};
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west = search {inherit pos; dir = dirs.west;};
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} |> lib.filterAttrs (n: v: !isNull v.pos));
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})
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|> listToAttrs;
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notNull = value: !isNull value;
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nodeGraph = graph: pkgs.runCommand "graph" {} ''
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mkdir -p $out
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echo 'digraph {
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${graph |> mapAttrs (from: edges:
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edges |> mapAttrs (dir: edge: if isNull edge.pos or null then "" else ''
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"${from}" -> "${edge.pos}" [label="${dir} ${toString edge.dist}"]
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'') |> attrValues |> concatStringsSep "\n"
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) |> attrValues |> concatStringsSep "\n"}
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}' > $out/graph.dot
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cat $out/graph.dot | ${pkgs.graphviz}/bin/dot -Tsvg > $out/graph.svg
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'';
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graphs = {
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corners = nodeGraph corners;
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};
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initScores = {
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${key init.pos} = {
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dir = "east";
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steps = 0;
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dist = 0;
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turns = 0;
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pos = key init.pos;
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};
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};
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getLowest = state: let
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unvisited = removeAttrs state.scores state.done;
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in
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attrValues unvisited |> foldl' (acc: node:
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if isNull acc.steps then node else
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if isNull node.steps then acc else
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if acc.steps < node.steps then acc else node
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) {turns = null; steps = null;}
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;
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getScores = {done ? [], scores ? initScores}: let
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prev = getLowest {inherit done scores;};
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in
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corners.${prev.pos}
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|> mapAttrs (dir: edge: let
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turns = if prev.dir == dir then prev.turns else prev.turns + 1;
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existing = scores.${edge.pos} or null;
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steps = prev.steps + edge.dist;
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# can't evaluate same turns
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# because we don't know where we will turn next.
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sameSteps = notNull existing
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&& existing.steps == steps
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;
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isBetter = isNull existing ||
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(existing.steps > steps);
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newScore = {
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inherit steps dir turns;
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inherit (edge) pos dist;
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prev = prev.pos;
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};
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in {
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name = edge.pos;
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value = if sameSteps then
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existing // {alt = newScore;}
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else if isBetter
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then newScore
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else existing
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;
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})
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|> attrValues
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|> listToAttrs
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|> (newScores: {
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scores = scores // newScores;
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done = done ++ [prev.pos];
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})
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;
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fastest = goal: s: let
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next = getScores s;
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in if elem (key goal) (next.done) then next else fastest goal next;
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pathScore = steps: turns: steps + turns * 1000;
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toGoal = (fastest init.goal {}).scores.${key init.goal};
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part1result = pathScore toGoal.steps toGoal.turns;
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# PART 2
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# WIP:
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# go through the path, add each pos to visited
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# if point has alt,
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# TODO: and the alt turns add up to the correct path.
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# find points on that path.
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# add length of filtered alt, (-1 for the overlap at end?).
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# add alt to visited.
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pathToList = scores: {pos ? key init.goal, visited ? []}:
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let
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res = scores.${pos};
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prevPath = if res ? prev
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then pathToList scores {pos = res.prev; visited = visited;}
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else {path = []; visited = [pos];};
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a = pathToList scores {pos = res.alt.prev; visited = visited ++ prevPath.visited;};
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altPath = if res ? alt
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then {path = [thisAltSpot] ++ a.path; inherit (a) visited;}
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else {path = []; visited = [];}
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;
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thisSpot = {inherit (res) pos steps turns dir dist;
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# alt = altPath.path;
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};
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thisAltSpot = {inherit (res.alt) pos steps turns dir dist;
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alt = [];
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};
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in {
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visited = [pos] ++ prevPath.visited ++ altPath.visited;
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path =
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if elem pos visited then [] else
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[thisSpot]
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++
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prevPath.path
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;
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};
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cornerScores = fastest init.goal {};
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addDist = foldl' (acc: {dist,alt,dir,...}:
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acc + dist + (if addDist alt == 1 then 0 else (addDist alt) - 2)
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) 1;
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part1path = (pathToList cornerScores.scores {});
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# not 520, too high
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part2resultWrong = addDist part1path.path;
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genChart = size: walls: path: genList (y: genList (x:
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if elem {inherit x y;} walls then "#"
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else if elem (key {inherit x y;}) (map ({pos,...}: pos) path) then "O"
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else "."
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) size) size;
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}
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