advent-of-code-2023/day3/solution.ts

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2023-12-05 01:38:49 +00:00
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];
/**
* 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);
}
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function isPartNumber(
components: Component[],
component: Component,
) {
return Boolean(
components.find((c) => isAdjacent(component, c) && c[2] !== "."),
);
}
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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();