Advent of Code 2021 - Day 3

advent.2021.3.clean.js

const lines = `
101000111100
000011111101
011100000100
100100010000
.
.
.
`.trim().split('\n');

function calculateCount(lines) {
	const count = [];

	lines.forEach((line) => {
		Array.from(line).forEach((digit, digitIndex) => {
			count[digitIndex] ||= [0, 0];
			count[digitIndex][+digit]++;
		});
	});

	return count;
}

const gammaRate = calculateCount(lines)
	.map(([zerosCount, onesCount]) => (zerosCount > onesCount ? '0' : '1'))
	.join('');

const epsilonRate = calculateCount(lines)
	.map(([zerosCount, onesCount]) => (zerosCount > onesCount ? '1' : '0'))
	.join('');

const powerConsumption = parseInt(gammaRate, 2) * parseInt(epsilonRate, 2);

function calculateRating(array, shouldKeepLine, digitIndex = 0) {
	if (array.length === 1 || digitIndex === array[0].length) return array[array.length - 1];

	const count = calculateCount(array);
	const newArray = array.filter((line) => shouldKeepLine(line[digitIndex], ...count[digitIndex]));

	if (!newArray.length) return array[array.length - 1];
	return calculateRating(newArray, shouldKeepLine, digitIndex + 1);
}

const oxygenGeneratorRating = calculateRating(
	lines,
	(digit, zerosCount, onesCount) => digit === (onesCount >= zerosCount ? '1' : '0')
);

const co2ScrubberRating = calculateRating(
	lines,
	(digit, zerosCount, onesCount) => digit === (zerosCount <= onesCount ? '0' : '1')
);

const lifeSupportRating = parseInt(oxygenGeneratorRating, 2) * parseInt(co2ScrubberRating, 2);

console.log({ powerConsumption, lifeSupportRating });