264 lines
7.2 KiB
Nix
264 lines
7.2 KiB
Nix
{lib, pkgs, ...}: input: 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;
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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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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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index2d fwd init.chart == "#"
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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 1 (init.width - 3) |> map (x:
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range 1 (init.height - 3) |> 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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# pos = key pos;
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};
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})
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|> listToAttrs;
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notNull = value: !isNull value;
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###### collecting continuous corners, doesn't work.
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countDirs = {north ? null, south ? null, east ? null, west ? null, ...}:
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[north south east west]
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|> filter (dir: notNull dir && notNull dir.pos)
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|> length
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;
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continue = prev: {dirs, dist ? 0}: let
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dir = if prev == "north" then "south" else
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if prev == "south" then "north" else
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if prev == "west" then "east" else
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if prev == "east" then "west" else
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throw "${toString prev} is not a direction!";
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prevEdge = dirs.${dir};
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in
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dirs |> lib.attrsToList |> lib.findFirst (
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{name, value}: !(name == dir) && !(isDead value)
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) null
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|> (res: res.value // {dir = res.name;})
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|> (next: let
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nextCorner = corners.${next.pos};
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in
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if isDead nextCorner || isDeadend nextCorner then null else
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if isNode nextCorner
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then next // {dist = next.dist + dist + prevEdge.dist + 1000;}
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else continue next.dir {
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dirs = nextCorner;
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dist = dist + prevEdge.dist + 1000;
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}
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)
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;
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isDead = corner: corner.pos or null == null;
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isNode = corner: let c = countDirs corner; in isTerminal corner || c > 2 || c == 1;
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isTerminal = corner: corner.pos == key init.goal || corner.pos == key init.pos;
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isDeadend = corner: let c = countDirs corner; in c == 1;
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nodes = corners |> mapAttrs (start: corner:
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joinNodes corner
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);
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joinNodes = corner:
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corner |> mapAttrs (dir: next:
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if isDead next || isDeadend next
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then null
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else if !isNode corners.${next.pos}
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then continue dir {dirs = corners.${next.pos};}
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else
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next // {inherit dir;})
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|> lib.filterAttrs (n: v: notNull v)
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;
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########
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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 > $out/graph.svg
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'';
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graphs = {
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corners = nodeGraph corners;
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nodes = nodeGraph nodes;
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};
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initScores = {
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${key init.pos} = {
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dir = "east";
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steps = 0;
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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.turns then node else
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if isNull node.turns then acc else
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if acc.turns < node.turns 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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sameSteps = notNull existing
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&& existing.steps == steps
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# && turns == existing.turns
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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;
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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.${key init.goal};
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part1result = pathScore toGoal.steps toGoal.turns;
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# PART 2
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# WIP:
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# go through the path, add each pos to visited
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# if point has alt, find points on that path not visited yet.
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# add length of filtered alt, (-1 for the overlap at end?).
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# add alt to visited.
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pathToList = scores: pos:
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let
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res = scores.${pos};
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prevPath = if res ? prev then pathToList scores res.prev else [];
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fullaltPath = pathToList scores res.alt.prev;
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joinIndex = findFirstIndex ({pos,...}: !elem pos (map ({pos, ...}: pos) prevPath)) null fullaltPath;
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altPath = lib.sublist (joinIndex - 1) (length fullaltPath) fullaltPath;
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thisSpot = {inherit (res) pos steps turns dir; };
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in
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prevPath
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++
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[(thisSpot // {
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alt = if res ? alt then altPath ++ [thisSpot] else null;
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})]
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;
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cornerScores = fastest init.goal {};
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part1path = (pathToList cornerScores.scores (key init.goal));
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}
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