67 lines
1.7 KiB
JavaScript
67 lines
1.7 KiB
JavaScript
import { readFileSync } from 'node:fs';
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const input = readFileSync('input', 'utf-8');
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function priorityForItem(item) {
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const c = item.charCodeAt(0);
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return c - (c >= 97 ? 96 : 38)
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}
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const rucksacks = input
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.split('\n')
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.filter(line => {
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if (!line) return false;
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if (line.length % 2 !== 0) {
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throw new Error('Rucksack with unequal compartments');
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}
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return true;
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})
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.map(line => line.split(''))
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.map(rucksack => ([
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// compartment 1
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rucksack.slice(0, rucksack.length / 2),
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// compartment 2
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rucksack.slice(rucksack.length / 2)
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]));
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const sumOfPriorities = rucksacks
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.map(([compartment1, compartment2]) => {
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const commonItems = [...new Set(
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compartment1.filter(item => compartment2.includes(item))
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)];
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if (commonItems.length !== 1) {
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throw new Error('Unexpected number of common items');
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}
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return priorityForItem(commonItems[0]);
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})
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.reduce((total, priority) => total + priority, 0);
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console.log(`Sum of priorities of common items: ${sumOfPriorities}`);
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const elfRucksackGroups = rucksacks
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.reduce((groups, rucksack) => {
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let group = groups[groups.length - 1];
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if (group.length >= 3) {
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group = [];
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groups.push(group);
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}
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group.push(rucksack);
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return groups;
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}, [[]]);
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const commonItemsInGroup = elfRucksackGroups
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.map(group => group
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.reduce((itemsA, itemsB) => {
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itemsA = [...new Set(itemsA.flat())];
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itemsB = [...new Set(itemsB.flat())];
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return itemsA.filter(item => itemsB.includes(item))
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})
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)
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const badgePriorities = commonItemsInGroup
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.map(items => priorityForItem(items[0]))
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.reduce((total, priority) => total + priority, 0)
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console.log(`Sum of badge priorities: ${badgePriorities}`);
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