import { readFileSync } from "fs"; const t0 = performance.now(); const input = readFileSync("input.txt") .toString() .split("\n") .filter((e) => e.length > 0); const instructions = input[0].split(""); const maps = input.slice(1).map((a) => { const [name, pair] = a.split(" = "); const mapping = pair.match(/^\(([A-Z]{3}), ([A-Z]{3})\)$/); const [_, L, R] = mapping; return { name, mapping: { L, R } }; }); const cycles = maps .filter((e) => e.name.endsWith("A")) .map((e) => { let count = 0, index = 0; let current = e; while (!current.name.endsWith("Z")) { const direction = instructions[index]; const mapping = current.mapping[direction]; current = maps.find((a) => a.name === mapping); index = (index + 1) % instructions.length; count++; } return { start: e, end: current, length: count }; }); const sizes = cycles.map((e) => e.length); const gcd = (a, b) => (b == 0 ? a : gcd(b, a % b)); const lcm = (a, b) => (a / gcd(a, b)) * b; const total = sizes.reduce(lcm, 1); console.log(total); const t1 = performance.now(); console.log(`Runtime: ${t1 - t0}ms`);