76 lines
2.7 KiB
Nix
76 lines
2.7 KiB
Nix
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let
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# Import nixpkgs lib and input file
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inherit ((builtins.getFlake (builtins.toString ./..)).inputs.nixpkgs) lib;
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input = builtins.readFile (builtins.toString ./input.txt);
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# Define functions
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matElem = row: col: mat: builtins.elemAt (builtins.elemAt mat row) col;
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matDet = m: ((matElem 0 0 m) * (matElem 1 1 m)) - ((matElem 0 1 m) * (matElem 1 0 m));
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# Parse input
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split = builtins.map
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(s:
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let
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split = lib.strings.splitString "\n" s;
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in { a = builtins.elemAt split 0; b = builtins.elemAt split 1; prize = builtins.elemAt split 2; }
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)
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(lib.strings.splitString "\n\n" input);
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extracted = builtins.map
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({ a, b, prize }: {
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a = lib.strings.splitString ", Y+" (builtins.substring 12 (-1) a);
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b = lib.strings.splitString ", Y+" (builtins.substring 12 (-1) b);
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prize = lib.strings.splitString ", Y=" (builtins.substring 9 (-1) prize);
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}) split;
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numbered = builtins.map
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({ a, b, prize }: {
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a = { x = lib.strings.toInt (builtins.elemAt a 0); y = lib.strings.toInt (builtins.elemAt a 1); };
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b = { x = lib.strings.toInt (builtins.elemAt b 0); y = lib.strings.toInt (builtins.elemAt b 1); };
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prize = { x = lib.strings.toInt (builtins.elemAt prize 0); y = lib.strings.toInt (builtins.elemAt prize 1); };
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}) extracted;
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# Solve system of equations
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mathified = builtins.map
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({ a, b, prize }: {
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# First equation
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a1 = a.x;
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b1 = b.x;
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c1 = prize.x;
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# Second equation
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a2 = a.y;
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b2 = b.y;
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c2 = prize.y;
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}) numbered;
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determinants = builtins.map
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({ a1, b1, c1, a2, b2, c2 }: {
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numerators = {
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a = matDet [
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[ c1 b1 ]
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[ c2 b2 ]
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];
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b = matDet [
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[ a1 c1 ]
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[ a2 c2 ]
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];
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};
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denominator = matDet [
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[ a1 b1 ]
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[ a2 b2 ]
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];
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}) mathified;
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tokens = (
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lib.lists.foldr
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({ numerators, denominator }: accumulated-tokens:
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accumulated-tokens + (
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if (
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(lib.trivial.mod numerators.a denominator) != 0
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|| (lib.trivial.mod numerators.b denominator) != 0
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)
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then 0
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else (numerators.a / denominator) * 3 + (numerators.b / denominator)
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)
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)
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0
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) determinants;
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output = tokens;
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in output
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