From 562768449425cf66eb786f942bf5add57d18e846 Mon Sep 17 00:00:00 2001
From: Luke Else <mail@luke-else.co.uk>
Date: Fri, 8 Dec 2023 16:23:24 +0000
Subject: [PATCH] Day 08 Part 2 complete :) Very efficient solution

---
 src/solutions/day08.rs | 16 +++++++++++-----
 src/utils.rs           | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/src/solutions/day08.rs b/src/solutions/day08.rs
index 5bc5c4b..da037d2 100644
--- a/src/solutions/day08.rs
+++ b/src/solutions/day08.rs
@@ -1,5 +1,7 @@
 use std::collections::HashMap;
 
+use crate::utils::{self};
+
 use super::Solution;
 
 pub struct Day08 {}
@@ -38,14 +40,17 @@ impl Solution for Day08 {
             }
         }
 
-        let mut count = 0u32;
+        let mut count = vec![];
 
-        println!("{:?}", start_points);
         for start in start_points {
-            count += self.traverse_to_end(&start, &"Z".to_owned(), &instructions, &map)?
+            count.push(self.traverse_to_end(&start, &"Z".to_owned(), &instructions, &map)?);
         }
 
-        Ok(Box::new(count))
+        let lcm = count
+            .iter()
+            .fold(1u64, |acc, x| -> u64 { utils::lcm(acc, *x as u64) });
+
+        Ok(Box::new(lcm))
     }
 
     fn get_day(&self) -> u8 {
@@ -87,6 +92,7 @@ impl Day08 {
         &self,
         start: &String,
         end: &String,
+        // detect_cycles: bool,
         instructions: &String,
         map: &HashMap<String, (String, String)>,
     ) -> Result<u32, Box<dyn std::error::Error>> {
@@ -105,7 +111,7 @@ impl Day08 {
                         continue;
                     }
                 }
-                if next.ends_with("ZZZ") {
+                if next.ends_with(end) {
                     found = true;
                     break;
                 }
diff --git a/src/utils.rs b/src/utils.rs
index fbe3c16..860be43 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -33,3 +33,27 @@ pub fn get_input(day: u8, input: InputType) -> Result<Vec<String>, Box<dyn Error
 
     Ok(data)
 }
+
+pub fn lcm(first: u64, second: u64) -> u64 {
+    first * second / gcd(first, second)
+}
+
+pub fn gcd(first: u64, second: u64) -> u64 {
+    let mut max = first;
+    let mut min = second;
+    if min > max {
+        let val = max;
+        max = min;
+        min = val;
+    }
+
+    loop {
+        let res = max % min;
+        if res == 0 {
+            return min;
+        }
+
+        max = min;
+        min = res;
+    }
+}