Advent Of Code 2017

Day1Solution.js

// Day 1 - Challenge #1
input.split('').reduce((acc, d, i, a) => {
	const n1 = Number(d);
	const n2 = Number(a[i+1] || a[0]);
	return (n1 === n2 ? acc + n1 : acc);
}, 0);

// Day 1 - Challenge #2
input.split('').reduce((acc, d, i, a) => {
	const n2Pos = (i + (a.length / 2)) % a.length;
	const n1 = Number(d);
	const n2 = Number(a[n2Pos]);
	return (n1 === n2 ? acc + n1 : acc);
}, 0);

Day2Solution.js

// Day 2 - Challenge #1
// input preformatted to => [[1,2,3],[4,5,6],etc]
input
    .map(numList => Math.max.apply(null, numList) - Math.min.apply(null, numList))
    .reduce((acc, num) => acc + num, 0);

// Day2 - Challenge #2
input.reduce((acc, numList) => {
    return acc + numList.reduce((acc2, n, i, a) => {
        const num2 = a.find(n2 => n !== n2 && n2 % n === 0);
        if (num2 != null) { acc2 = num2 / n; }
        return acc2;
    }, 0);
}, 0);

Day3Solution.js

// Day 3 - Challenge #1
function getDist(num) {
	let sqrt = Math.ceil(Math.sqrt(num));
	let sideLengthOfSq = (sqrt % 2 === 0 ? sqrt + 1 : sqrt);
	let highestNumInSq = sideLengthOfSq * sideLengthOfSq;
	let targetDistFromCorner = (highestNumInSq - num) % (sideLengthOfSq - 1);
	let targetDistFromSideCenter = Math.abs(targetDistFromCorner - Math.floor(sideLengthOfSq/2));
	const closestDistFromSq = (sideLengthOfSq - 1) / 2;
	return closestDistFromSq + targetDistFromSideCenter;
}