From e57d0b97c8cb365d7d0a3ee7a0fc9294d2c8dcee Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Sat, 9 Dec 2023 02:23:56 +0300
Subject: feat(day-8): add part 2 solution
---
day-8/script.ts | 49 ++++++++++++++++++++++++++++++++-----------------
1 file changed, 32 insertions(+), 17 deletions(-)
(limited to 'day-8')
diff --git a/day-8/script.ts b/day-8/script.ts
index 71849c7..87e33cd 100644
--- a/day-8/script.ts
+++ b/day-8/script.ts
@@ -1,5 +1,13 @@
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()
@@ -17,26 +25,33 @@ const nodes = lines
};
})
.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 targetNumber = lines.findIndex((line) => line.startsWith("ZZZ"));
-let currentNumber = lines.findIndex((line) => line.startsWith("AAA"));
-
-let steps = 0;
-while (currentNumber !== targetNumber) {
- const direction = (
- {
- L: "left",
- R: "right",
- } as const
- )[directions[steps % directions.length]];
- if (!direction) throw new Error("Invalid direction");
-
- currentNumber = nodes[currentNumber][direction];
- steps++;
-}
+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({ steps });
+console.log({ result });
--
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