54 lines
1.4 KiB
JavaScript
54 lines
1.4 KiB
JavaScript
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import { readFileSync } from 'node:fs';
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const input = readFileSync('input', 'utf-8');
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const pairs = input
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.split('\n\n')
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.map(pair => pair
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.split('\n')
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.filter(line => line)
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.map(line => JSON.parse(line))
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);
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export function compare(left, right) {
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const leftIsArray = Array.isArray(left);
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const rightIsArray = Array.isArray(right);
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const compareArrays = leftIsArray || rightIsArray;
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if (leftIsArray && !rightIsArray) {
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right = [right];
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}
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if (rightIsArray && !leftIsArray) {
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left = [left];
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}
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if (compareArrays) {
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for (let i = 0; i < Math.max(left.length, right.length); i++) {
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if (i >= left.length) return -1;
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if (i >= right.length) return 1;
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const result = compare(left[i], right[i]);
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if (result !== 0) return result;
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}
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return 0;
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} else {
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return (left - right) / Math.abs(left - right || 1);
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}
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}
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const sumOfIndices = pairs
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.map(([left, right], i) => [i + 1, compare(left, right)])
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.filter(([_index, result]) => result === -1)
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.reduce((total, [index, _result]) => total + index, 0);
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console.log(`Sum of correctly ordered inices: ${sumOfIndices}`);
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const dividerPackets = [[[2]], [[6]]];
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const allPackets = [...pairs.flat(), ...dividerPackets];
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allPackets.sort(compare);
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const decoderKey = dividerPackets
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.map(packet => allPackets.indexOf(packet) + 1)
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.reduce((total, index) => total * index);
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console.log(`Decoder key: ${decoderKey}`);
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