42 lines
1.3 KiB
JavaScript
42 lines
1.3 KiB
JavaScript
function day14(input, part2) {
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input = input.split("\n").splitOnElement("")
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let init = input[0][0].split("")
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let rules = input[1].map((e) => e.split(" -> "))
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let counts = {}
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for (let i = 0; i < init.length - 1; i++) {
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let substr = init[i] + init[i + 1]
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counts[substr] = (counts[substr] || 0) + 1
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}
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for (let i = 0; i < (part2 ? 40 : 10); i++) {
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let changes = {}
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for (let rule of rules) {
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let target = rule[0][0] + rule[0][1]
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let left = rule[0][0] + rule[1]
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let right = rule[1] + rule[0][1]
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changes[left] = (changes[left] || 0) + (counts[target] || 0)
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changes[right] = (changes[right] || 0) + (counts[target] || 0)
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changes[target] = (changes[target] || 0) - (counts[target] || 0)
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}
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for (let pair in changes) {
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counts[pair] = (counts[pair] || 0) + changes[pair]
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}
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}
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counts = Object.keys(counts).map((key) => [key.split(""), counts[key]])
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let letters = counts.flatMap((e) => e[0]).uniq().map((letter) => (counts.filter((e) => e[0].includes(letter)).map((e) => e[0].count(letter) * e[1]).sum() + (letter == init[0] || letter == init[init.length - 1])) / 2)
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return letters.max() - letters.min()
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}
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if (typeof window == "undefined") {
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module.exports = day14
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}
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