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2024 day 18 part 2

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Tristan 2024-12-18 23:12:50 +00:00
parent 5467ea9393
commit 5d8d809844
2 changed files with 53 additions and 28 deletions
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32
2024/18/solution.nix
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@ -1,7 +1,8 @@
{lib, input ? "", my-lib, ...}@pkgs: rec {
inherit pkgs;
inherit lib;
inherit (builtins) elemAt genList elem concatStringsSep;
inherit my-lib;
inherit (builtins) elemAt genList elem concatStringsSep length;
inherit (lib) splitString;
inherit (lib.strings) toIntBase10;
@ -21,18 +22,39 @@
chartToStr = chart: chart |> (map (concatStringsSep "")) |> concatStringsSep "\n";
inherit (my-lib.dijkstra {}) key;
mkSolution = {size, bytes, input}: rec {
inherit size bytes input;
walls = lib.sublist 0 bytes (init input);
chart = genChart size walls;
part1result = dijkstra.toGoal.steps;
dijkstra = my-lib.dijkstra {
walls = init input;
part1result = p1Dijkstra.toGoal.steps;
p1Dijkstra = searchAfterBytes 12;
searchAfterBytes = bytes: let
walls = lib.sublist 0 bytes (init input);
chart = genChart size walls;
in my-lib.dijkstra {
pos = {x = 0; y = 0;};
goal = {x = size - 1; y = size - 1;};
chart = chart;
width = size;
height = size;
};
findFirst = bytes: prevPath: let
dijkstra = lib.traceSeq "retracing after ${toString bytes} with ${key wall}" (searchAfterBytes bytes);
wall = elemAt walls (bytes - 1);
wallCollides = elem (key wall) (map ({pos,...}: pos) prevPath);
in if !wallCollides
then findFirst (bytes + 1) prevPath
else
if dijkstra.isImpossible
then key wall
else
findFirst (bytes + 1) dijkstra.path;
part2result = findFirst bytes p1Dijkstra.path;
};
example = mkSolution {