import fs from "fs";

function gcd(a: number, b: number) {
  return !b ? a : gcd(b, a % b);
}

function lcm(a: number, b: number) {
  return (a * b) / gcd(a, b);
}

const [directions, _, ...lines] = fs
  .readFileSync("./input.txt")
  .toString()
  .split("\n")
  .slice(0, -1);

const nodes = lines
  .map((line) => {
    const match = line.match(/(...) = \((...), (...)\)/);
    if (!match) throw new Error("Could not match");
    return {
      node: match[1],
      left: match[2],
      right: match[3],
    };
  })
  .map((node, index, nodes) => ({
    name: node.node,
    node: index,
    left: nodes.findIndex((n) => n.node === node.left),
    right: nodes.findIndex((n) => n.node === node.right),
  }));

const [startingNodes, terminalNodes] = ["A", "Z"].map((char) =>
  nodes.filter((n) => n.name.endsWith(char)).map((n) => n.node),
);

const result = startingNodes
  .map((node) => {
    let steps = 0;
    while (!terminalNodes.includes(node)) {
      const direction = (
        {
          L: "left",
          R: "right",
        } as const
      )[directions[steps % directions.length]];
      if (!direction) throw new Error("Invalid direction");

      node = nodes[node][direction];
      steps++;
    }
    return steps;
  })
  .reduce((acc, x) => lcm(acc, x), 1);

console.log({ result });