57 lines
1.9 KiB
Nix
57 lines
1.9 KiB
Nix
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{lib, ...}: input: rec {
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inherit lib;
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inherit (lib) splitString mod;
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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;
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index = i: list: elemAt list i;
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index2d = {x, y}: m: m |> index y |> index x;
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init = let
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chart = input |> splitString "\n" |> map stringToCharacters;
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width = (elemAt chart 0 |> length) + 1;
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height = length chart;
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startIndex = input |> stringToCharacters |> findFirstIndex (char: char == "S") null;
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endIndex = input |> stringToCharacters |> findFirstIndex (char: char == "E") null;
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in {
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inherit chart width height;
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pos = {
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x = mod startIndex width;
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y = startIndex / width;
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};
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goal = {
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x = mod endIndex width;
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y = endIndex / width;
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};
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}
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;
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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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minl = foldl' (a: e: if isNull a then e else if isNull e then a else if a < e then a else e) null;
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search = {pos ? init.pos, dir ? {x = 1; y = 0;}, hist ? [], max ? null}:
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let
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fwd = search {pos = addVec pos dir; inherit dir; hist = hist ++ [{inherit pos dir;}];} |> add 1;
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rot = search {inherit pos; dir = rotate dir; hist = hist ++ [{inherit pos dir;}]; max = fwd;} |> add 1000;
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rot' = search {inherit pos; dir = rotate' dir; hist = hist ++ [{inherit pos dir;}]; max = fwd;} |> add 1000;
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add = n: a: if isNull a then null else n + a;
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in
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if pos == init.goal then 0 else
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if
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elem {inherit pos dir;} hist ||
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elem {inherit pos; dir = multVec dir (-1);} hist ||
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index2d pos init.chart == "#" then null else
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minl [fwd rot rot']
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;
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}
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