From 63aae6749ded480eee0bf898c492c6ed1b0e1ca0 Mon Sep 17 00:00:00 2001
From: TobenderZephyr <marcus@dre.ist>
Date: Sat, 21 Dec 2024 11:50:36 +0100
Subject: [PATCH] day 08 part 2 updated with LCM. No more brute forcing

---
 2023/day08/index.js | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/2023/day08/index.js b/2023/day08/index.js
index f7ffcb6..be3a9d5 100644
--- a/2023/day08/index.js
+++ b/2023/day08/index.js
@@ -33,7 +33,7 @@ class DesertMap {
         }
         return this.#route.find(route => route.from === from)[towards]
     }
-    navigate_ghosts() {
+    navigate_brute() {
         this.setup()
         let i = 0
         let start = this.#route.filter(route => route.from[2] === 'A')
@@ -50,6 +50,34 @@ class DesertMap {
         console.log(this.steps + 1)
     }
 
+    lcm(numbers) {
+        function gcd(a, b) {
+            if (b === 0) {
+                return a;
+            }
+            return gcd(b, a % b);
+        }
+        return numbers.reduce((a, b) => a * b / gcd(a, b));
+    }
+
+    navigate_ghosts() {
+        this.setup()
+        let routes = this.#route.filter(route => route.from[2] === 'A')
+            .map(route => route.from)
+        let results = routes.map(route => {
+            let i = 0
+            let steps = 0
+            while (i < this.instructions.length | true) {
+                route = this.run(this.instructions[i], route)
+                ++steps
+                if (route[2] === 'Z') { return steps }
+                i = this.instructions.length - i === 1 ? 0 : i + 1
+            }
+        })
+        console.log(`LCM of ${results.join(", ")}`)
+        console.log(this.lcm(results))
+    }
+
     navigate() {
         this.setup()
         let i = 0