28 lines
850 B
Nix
28 lines
850 B
Nix
with import ../util.nix;
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let
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# read input
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input = readFile ./input;
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bags = map (line: toPriority (stringToCharacters line)) (splitString "\n" input);
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# converts item symbol to numerical priority
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toPriority = l: map (c:
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if c == toLower c then (charToInt c) - (charToInt "a") + 1
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else (charToInt c) - (charToInt "A") + 27
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) l;
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# split bags into their two compartments
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compartments = map (contents: cutInHalf contents) bags;
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# find the item in common for the input bags/compartments
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findCommonItem = l: head (intersectManyLists l);
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# common items between the compartments per bag
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commonItems = map findCommonItem compartments;
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# common items between the bags per group of three elfs
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commonItemsInElfGrp = map findCommonItem (chunksOf 3 bags);
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in {
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part1 = sum commonItems;
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part2 = sum commonItemsInElfGrp;
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} |