114 lines
3.1 KiB
Nix
114 lines
3.1 KiB
Nix
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{ pkgs, lib }:
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with lib;
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let
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calculateTreeVisibilityForLine = line: let
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updateState = { currentMax ? (-1), trees ? [] }: tree:
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if tree > currentMax then { currentMax = tree; trees = trees ++ [true]; }
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else { inherit currentMax; trees = trees ++ [false]; };
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forwards = (foldl updateState { } line).trees;
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backwards = reverseList (foldr (flip updateState) { } line).trees;
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in zipListsWith or forwards backwards;
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transpose = grid:
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genList (n: map ((flip elemAt) n) grid) (length grid);
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combineGridsWith = f: grid1: grid2: let
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height = length grid1;
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width = length (elemAt grid1 0);
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elemAt' = row: col: grid: elemAt (elemAt grid row) col;
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generator = row: col: f (elemAt' row col grid1) (elemAt' row col grid2);
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in genList (row: genList (col: generator row col) width) height;
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trees = pipe ./input.txt [
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fileContents
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(splitString "\n")
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(map (splitString ""))
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(map tail)
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(map init)
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(map (map toInt))
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];
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treeVisibleGrid = pipe trees [
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(lines: { horizontal = lines; vertical = transpose lines; })
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(mapAttrs (_: map calculateTreeVisibilityForLine))
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({horizontal, vertical}: { inherit horizontal; vertical = transpose vertical; })
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({horizontal, vertical}: combineGridsWith or horizontal vertical)
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];
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visualization = let
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genColor = name: command: builtins.readFile
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(pkgs.runCommand name {
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buildInputs = [ pkgs.ncurses ];
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} "tput ${command} > $out");
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red = genColor "red" "setaf 1";
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green = genColor "green" "setaf 2";
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clear = genColor "clear" "sgr0";
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greenRedTree = visible: tree:
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if visible then "${green}${tree}${clear}"
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else "${red}${tree}${clear}";
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in pipe trees [
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(map (map toString))
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(combineGridsWith greenRedTree treeVisibleGrid)
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(map (concatStringsSep ""))
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(concatStringsSep "\n")
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];
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answer1 = pipe treeVisibleGrid [
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(map (count id))
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(foldr add 0)
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toString
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];
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countUntil = stopPred: xs:
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if xs == [] then 0
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else if stopPred (head xs) then 1
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else 1 + (countUntil stopPred (tail xs));
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visibleDistanceBackwards = line: let
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measure = trees: size: let
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newTree = {
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inherit size;
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viewDistance = countUntil (x: x.size >= size) trees;
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};
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in [newTree] ++ trees;
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in pipe line [
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(foldl measure [])
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(map (x: x.viewDistance))
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reverseList
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];
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visibleDistanceHorizontal = line: let
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backwards = visibleDistanceBackwards line;
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forwards = pipe line [
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reverseList
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visibleDistanceBackwards
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reverseList
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];
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in zipListsWith (x: y: x * y) forwards backwards;
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answer2 = pipe trees [
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(lines: { horizontal = lines; vertical = transpose lines; })
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(mapAttrs (_: map visibleDistanceHorizontal))
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({horizontal, vertical}: { inherit horizontal; vertical = transpose vertical; })
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({horizontal, vertical}: combineGridsWith (x: y: x * y) horizontal vertical)
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(map (foldr max 0))
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(foldr max 0)
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toString
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];
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in pkgs.writeText "answers" ''
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Task1:
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${answer1}
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Visualization:
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${visualization}
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Task2:
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${answer2}
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''
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