Finished part 2. Not really satisfied with the answer.

day_08/Cargo.lock

@@ -181,6 +181,8 @@ version = "0.1.0"
 dependencies = [
  "criterion",
  "nom",
+ "num",
+ "rayon",
  "strum",
  "strum_macros",
 ]
@@ -301,6 +303,73 @@ dependencies = [
  "minimal-lexical",
 ]
 
+[[package]]
+name = "num"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b05180d69e3da0e530ba2a1dae5110317e49e3b7f3d41be227dc5f92e49ee7af"
+dependencies = [
+ "num-bigint",
+ "num-complex",
+ "num-integer",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+]
+
+[[package]]
+name = "num-bigint"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-complex"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ba157ca0885411de85d6ca030ba7e2a83a28636056c7c699b07c8b6f7383214"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "225d3389fb3509a24c93f5c29eb6bde2586b98d9f016636dff58d7c6f7569cd9"
+dependencies = [
+ "autocfg",
+ "num-traits",
+]
+
+[[package]]
+name = "num-iter"
+version = "0.1.43"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d03e6c028c5dc5cac6e2dec0efda81fc887605bb3d884578bb6d6bf7514e252"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0638a1c9d0a3c0914158145bc76cff373a75a627e6ecbfb71cbe6f453a5a19b0"
+dependencies = [
+ "autocfg",
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.17"

day_08/Cargo.toml

@@ -7,6 +7,8 @@ edition = "2021"
 
 [dependencies]
 nom = "7.1.3"
+num = "0.4.1"
+rayon = "1.8.0"
 strum = "0.25.0"
 strum_macros = "0.25.3"
 

day_08/src/lib.rs

@@ -1,14 +1,11 @@
 use nom::{
-    bytes::complete::{take_until, take, tag},
+    bytes::complete::{take, tag},
-    character::complete::{
+    character::complete::alphanumeric1,
-        newline, multispace1, alphanumeric1,
-    },
     sequence::{preceded, separated_pair},
-    multi::separated_list1,
     IResult,
 };
 use std::collections::HashMap;
-use std::str::Chars;
+use num::integer::lcm;
 
 fn parse_mapline(input: &str) -> IResult<&str, (&str, (&str, &str))> {
     let (input, start) = take(3 as usize)(input)?;
@@ -40,29 +37,59 @@ pub fn part1(input: &str) -> String {
 }
 
 pub fn part2(input: &str) -> String {
+    // let mut lines = input.lines();
+    // let instructions = lines.next().unwrap().chars();
+    // let map = lines.skip(1).map(|line| {
+    //     parse_mapline(line).unwrap().1
+    // }).collect::<HashMap<&str, (&str, &str)>>();
+    // let start_nodes = map.keys().into_iter().filter(|x| x.chars().last().unwrap() == 'A').collect::<Vec<_>>();
+    // let mut total_steps = 0_u64;
+    // let mut positions = start_nodes;
+    // for _ in 0..1000000 {
+    //     for instruction in instructions.clone() {
+    //         total_steps += 1;
+    //         for i in 0..positions.len() {
+    //             let (left, right) = map.get(positions[i]).unwrap();
+    //             if instruction == 'L' {
+    //                 positions[i] = &left;
+    //             } else {
+    //                 positions[i] = &right;
+    //             }
+    //         }
+    //         if positions.iter().all(|x| {x.chars().last().unwrap() == 'Z'}) { return total_steps.to_string(); };
+    //     }
+    // };
+    // total_steps.to_string()
     let mut lines = input.lines();
     let instructions = lines.next().unwrap().chars();
     let map = lines.skip(1).map(|line| {
         parse_mapline(line).unwrap().1
     }).collect::<HashMap<&str, (&str, &str)>>();
     let start_nodes = map.keys().into_iter().filter(|x| x.chars().last().unwrap() == 'A').collect::<Vec<_>>();
-    let mut total_steps = 0;
+    let mut solutions = Vec::<u64>::new();
-    let mut positions = start_nodes;
+    for ind in 0..start_nodes.len() {
-    for _ in 0..10000000 {
+        let mut total_steps = 0;
-        for instruction in instructions.clone() {
+        let start_node = start_nodes[ind];
-            total_steps += 1;
+        let mut position = *start_node;
-            for i in 0..positions.len() {
+        for _ in 0..100000 {
-                let (left, right) = map.get(positions[i]).unwrap();
+            for instruction in instructions.clone() {
+                total_steps += 1;
+                let (left, right) = map.get(position).unwrap();
                 if instruction == 'L' {
-                    positions[i] = &left;
+                    position = left;
                 } else {
-                    positions[i] = &right;
+                    position = right;
                 }
+                if position.chars().last().unwrap() == 'Z' { break; };
             }
-            if positions.iter().all(|x| {x.chars().last().unwrap() == 'Z'}) { return total_steps.to_string(); };
+            if position.chars().last().unwrap() == 'Z' { break; };
-        }
+        };
-    };
+        solutions.push(total_steps);
-    total_steps.to_string()
+    }
+    println!("{:?}", &solutions);
+    let first = solutions[0];
+    solutions.into_iter().skip(1).fold(first, |acc, x| {lcm(acc, x)}).to_string()
+
 }
 
 pub mod prelude {