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