function blink(n) {
if (n === 0) {
return [1];
}
const len = Math.floor(Math.log10(n) + 1);
if (len % 2 === 0) {
const div = 10 ** (len / 2);
return [Math.floor(n / div), n % div];
}
return [n * 2024];
}
function parse(input) {
return input.split(/\s+/).map((d) => [Number(d), 1]);
}
function countStones(stones, n) {
for (let i = 0; i < n; i++) {
const freqs = new Map();
stones.forEach(([stone, freq]) => {
blink(stone).forEach((newStone) => {
freqs.set(newStone, (freqs.get(newStone) || 0) + freq);
});
});
stones = [...freqs.entries()];
}
return d3.sum(stones, (d) => d[1]);
}
function part1(input) {
return countStones(parse(input), 25);
}
function part2(input) {
return countStones(parse(input), 75);
}
Purpose-built for displays of data
Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
