Missed several updates. Working on 8 pt 2

day_08/src/lib.rs

@@ -0,0 +1,72 @@
+use nom::{
+    bytes::complete::{take_until, take, tag},
+    character::complete::{
+        newline, multispace1, alphanumeric1,
+    },
+    sequence::{preceded, separated_pair},
+    multi::separated_list1,
+    IResult,
+};
+use std::collections::HashMap;
+use std::str::Chars;
+
+fn parse_mapline(input: &str) -> IResult<&str, (&str, (&str, &str))> {
+    let (input, start) = take(3 as usize)(input)?;
+    let (input, (left, right)) = preceded(tag(" = ("), separated_pair(alphanumeric1, tag(", "), alphanumeric1))(input)?;
+    Ok((input, (start, (left, right))))
+}
+
+pub fn part1(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 mut total_steps = 0;
+    let mut position = "AAA";
+    for _ in 0..100 {
+        for instruction in instructions.clone() {
+            total_steps += 1;
+            let (left, right) = map.get(position).unwrap();
+            if instruction == 'L' {
+                position = left;
+            } else {
+                position = right;
+            }
+            if position == "ZZZ" { return total_steps.to_string(); };
+        }
+    };
+    total_steps.to_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;
+    let mut positions = start_nodes;
+    for _ in 0..10000000 {
+        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()
+}
+
+pub mod prelude {
+    pub use super::part1;
+    pub use super::part2;
+}
+