52 lines
1.3 KiB
TypeScript
52 lines
1.3 KiB
TypeScript
const fs = require('fs');
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const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
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let stones: Array<string> = input.slice(0, -1).split(' ');
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const countMap: { [key: string]: Array<number> } = {};
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let sum = 0;
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function getCountAfter(stone: string, blink: number, prev: Array<string> = []): number {
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const nextStep = blink - 1;
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if (countMap[stone]) {
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if (countMap[stone][nextStep]) {
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return countMap[stone][nextStep];
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}
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} else {
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countMap[stone] = [];
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}
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let newStones: Array<string>;
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if (stone === '0') {
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newStones = ['1'];
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} else {
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const len = stone.length;
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if (len % 2 === 0) {
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let last = stone.slice(len / 2);
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newStones = [stone.slice(0, len / 2), ''+parseInt(last)];
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} else {
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newStones = [''+(parseInt(stone) * 2024)];
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}
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}
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const len = newStones.length;
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countMap[stone][0] = len;
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if (blink === 1) {
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return len;
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} else {
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const newPrev = [...prev, stone];
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const len = newStones.reduce((carry, newStone) => carry + getCountAfter(newStone, nextStep, newPrev), 0);
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countMap[stone][nextStep] = len;
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return len;
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}
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}
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const blinks = 75;
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stones.forEach((stone) => {
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sum += getCountAfter(stone, blinks);
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});
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console.log(sum);
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