async function loadInput(filename: string) { const decoder = new TextDecoder("utf-8"); const contents = await Deno.readFile(filename); return decoder.decode(contents); } function toSubComponents(l: string) { const components: [number, string][] = []; let current = ""; let idx = 0; for (const c of l) { if ( current.length === 0 || !Number.isNaN(Number(current[0])) && !Number.isNaN(Number(c)) ) { current += c; } else { components.push([idx - current.length, current]); current = c; } idx++; } components.push([idx - current.length, current]); return components; } type Component = [number, number, string]; function isPartNumber( components: Component[], component: Component, ) { return Boolean( components.find((c) => isAdjacent(component, c) && c[2] !== "."), ); } /** * Checks whether two components are adjacent * @param c1 First component. * @param c2 Second component. */ function isAdjacent([y1, x1, s1]: Component, [y2, x2, s2]: Component) { const [l1, l2] = [s1.length, s2.length]; // end x positions const [x1e, x2e] = [x1 + l1 - 1, x2 + l2 - 1]; return (y1 === y2 - 1 || y1 === y2 + 1) && ( (x1 - 1 <= x2 && x2 <= x1e + 1) || (x1 - 1 <= x2e && x2e <= x1e + 1) || (x2 <= x1 - 1 && x1e + 1 <= x2e) ) || (y1 === y2) && (x2e === x1 - 1 || x2 === x1e + 1); } function gearRatio( components: Component[], component: Component, ) { if (component[2] !== "*") return null; const numbers = components .filter((c) => isAdjacent(component, c)) .map(([, , s]) => Number(s)) .filter((n) => !Number.isNaN(n)); if (numbers.length === 2) { return numbers[0] * numbers[1]; } return null; } async function main() { const lines = await loadInput("input.txt").then((s) => s.split("\n")); const components = lines.map(toSubComponents) .flatMap((cs, idx) => cs.map((c) => [idx, c[0], c[1]] as Component)); const numbers = components.filter(([, , s]) => !Number.isNaN(Number(s))); const fnumbers = numbers.filter((c) => isPartNumber(components, c)); console.log( "Part 1:", fnumbers.map(([, , s]) => Number(s)).reduce((p, c) => p + c), ); const gears = components .map((c) => gearRatio(components, c)) .filter((c) => c !== null) as number[]; console.log("Part 2:", gears.reduce((p, c) => p + c)); } await main();