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no bueno
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2023/day08/part2.ts
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2023/day08/part2.ts
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type Node = { L: string; R: string };
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type Network = Record<string, Node>;
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type Path = {
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possiblePaths: string[];
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};
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//
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export function answer(input: string) {
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const [instructions, , ...networkRaw] = input.split("\n");
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const network: Network = networkRaw.reduce((network, line) => {
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const [id, leftAndRight] = line.split(" = ");
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const [L, R] = leftAndRight.replaceAll(/[\(\)]/g, "").split(", ");
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return { ...network, [id]: { L, R } };
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}, {});
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const parseNetwork = (lines: string[]): Network =>
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lines.reduce((network, line) => {
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const [id, leftAndRight] = line.split(" = ");
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const [L, R] = leftAndRight.replaceAll(/[\(\)]/g, "").split(", ");
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return { ...network, [id]: { L, R } };
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}, {});
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const paths = Object.keys(network).filter((n) => n.endsWith("A"));
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return BigInt(
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paths
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.map((p) => countSteps(p, network, instructions))
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.reduce((total, x) => (total *= x), 1),
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);
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const network: Network = parseNetwork(networkRaw);
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// build the paths to X for each starting path
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// step forward by longest path
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// new positions are stepSize % pathSize
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const paths = Object.keys(network)
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.filter((n) => n.endsWith("A"))
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.map((p) => {
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const path = buildPath(p, network, instructions);
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console.log(`plength: ${path.length}, last: ${path[path.length - 1]}`);
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return { current: path.length - 1, path };
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});
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const stepSize = Math.max(...paths.map(({ path }) => path.length));
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let stepTotal = stepSize;
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while (!paths.every((p) => p.path[p.current] === "Z")) {
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console.log(`step by ${stepSize}`);
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paths.forEach((p) => {
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p.current += stepSize;
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p.current = p.path.length % p.current;
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console.log(p);
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});
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stepTotal += stepSize;
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}
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return stepTotal;
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}
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function countSteps(
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function buildPath(
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start: string,
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network: Network,
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instructions: string,
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): number {
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): string[] {
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let currentNode = start;
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let stepCount = 0;
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const endingChars = [start[2]];
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while (!currentNode.endsWith("Z")) {
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for (const dir of instructions.split("")) {
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currentNode = network[currentNode][dir as keyof Node];
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stepCount++;
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endingChars.push(currentNode[2]);
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if (currentNode.endsWith("Z")) break;
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}
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}
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return stepCount;
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return endingChars;
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}
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if (import.meta.main) {