37 lines
804 B
JavaScript
37 lines
804 B
JavaScript
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import fs from "fs";
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/**
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* Main function for Puzzle A
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*
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* @param {string} data - Puzzle input as a single string.
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*/
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async function main(data) {
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const input = data.split(",").map((num) => parseInt(num));
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/** @type {Map<number, number>} */
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const lastSaid = new Map();
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let prevSpoken = NaN;
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let spoken = NaN;
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for (let i = 0; i < input.length - 1; i++) {
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lastSaid.set(input[i], i);
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}
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spoken = input[input.length - 1];
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for (let i = input.length; i < 2020; i++) {
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prevSpoken = spoken;
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spoken = 0;
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if (lastSaid.has(prevSpoken))
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spoken = i - lastSaid.get(prevSpoken) - 1;
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lastSaid.set(prevSpoken, i - 1);
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}
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return spoken;
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}
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fs.readFile("input", (err, data) => {
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if (err) throw err;
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main(data.toString()).then(console.log).catch(console.error);
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});
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