day7 :))

src/day7.rs

@@ -0,0 +1,112 @@
+use std::collections::HashMap;
+
+#[aoc(day7, part1)]
+pub fn part1(input: &str) -> u32 {
+    let run = run(input);
+    run.0
+}
+
+#[aoc(day7, part2)]
+pub fn part2(input: &str) -> u64 {
+    let run = run(input);
+    run.1
+}
+
+fn run(input: &str) -> (u32, u64) {
+    let field = parse(input);
+    let mut beams = HashMap::new();
+    let mut split_count = 0_u32;
+    for field_slice in field {
+        let local_split;
+        (beams, local_split) = propagate(&field_slice, beams);
+        split_count = split_count + local_split;
+        //println!("{}", split_count);
+        println!("{:?}", beams);
+    }
+    let timeline_count = beams.values().sum();
+    (split_count, timeline_count)
+}
+
+#[derive(Clone, Debug)]
+enum TachyonPoint {
+    Source,
+    Splitter,
+}
+
+fn parse(input: &str) -> Vec<Vec<(usize, TachyonPoint)>> {
+    let lines = input.lines().filter(|l| l.chars().any(|c| c != '.'));
+    let mut fieldmap: Vec<Vec<(usize, TachyonPoint)>> = vec![Vec::new(); lines.clone().count()];
+
+    for (i, line) in lines.enumerate() {
+        // println!("{}", line);
+        for (j, c) in line.chars().enumerate() {
+            match c {
+                'S' => fieldmap[i].push((j, TachyonPoint::Source)),
+                '^' => fieldmap[i].push((j, TachyonPoint::Splitter)),
+                '.' => {}
+                _ => panic!("Unexpected input!"),
+            }
+        }
+    }
+    fieldmap
+}
+
+fn propagate(
+    field_slice: &Vec<(usize, TachyonPoint)>,
+    mut beams: HashMap<usize, u64>,
+) -> (HashMap<usize, u64>, u32) {
+    let mut split_count = 0;
+    for (i, tachyonpoint) in field_slice {
+        match tachyonpoint {
+            TachyonPoint::Source => {
+                beams.insert(*i, 1);
+            }
+            TachyonPoint::Splitter => {
+                if beams.contains_key(i) {
+                    split_count = split_count + 1;
+                    let local_value = beams[i];
+                    beams.remove(i);
+                    let left = beams.remove(&(i - 1)).unwrap_or(0_u64);
+                    beams.insert(i - 1, local_value + left);
+                    let right = beams.remove(&(i + 1)).unwrap_or(0_u64);
+                    beams.insert(i + 1, local_value + right);
+                }
+            }
+        }
+    }
+    (beams, split_count)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EXAMPLE_INPUT: &str = "\
+.......S.......
+...............
+.......^.......
+...............
+......^.^......
+...............
+.....^.^.^.....
+...............
+....^.^...^....
+...............
+...^.^...^.^...
+...............
+..^...^.....^..
+...............
+.^.^.^.^.^...^.
+...............
+";
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(EXAMPLE_INPUT), 21);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(EXAMPLE_INPUT), 40);
+    }
+}

src/lib.rs

@@ -8,6 +8,7 @@ extern crate aoc_runner_derive;
 // pub mod day3;
 // pub mod day4;
 // pub mod day5;
-pub mod day6;
+// pub mod day6;
+pub mod day7;
 
 aoc_lib! { year = 2025 }