solve: day 7

Author: tom-anders

Cargo.toml

@@ -2,7 +2,7 @@
 resolver = "2"
 members = [
     "aoc_lib/aoc_derive",
-    "aoc_lib/utils", "day1", "day2", "day3", "day4", "day5", "day6",
+    "aoc_lib/utils", "day1", "day2", "day3", "day4", "day5", "day6", "day7",
 ]
 
 [workspace.dependencies]

aoc_lib

@@ -0,0 +1,18 @@
+[package]
+name = "day7"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+aoc_derive.path = '../aoc_lib/aoc_derive'
+utils.path = '../aoc_lib/utils'
+derive_more.workspace = true
+itertools.workspace = true
+lazy-regex.workspace = true
+parse-display.workspace = true
+rayon.workspace = true
+regex.workspace = true
+num.workspace = true
+
+[dev-dependencies]
+pretty_assertions.workspace = true

day7/Cargo.toml

@@ -0,0 +1,72 @@
+use std::collections::HashMap;
+
+use aoc_derive::aoc_main;
+use utils::{OneOrTwo::*, grid::Grid, *};
+
+#[derive(Debug, Clone)]
+struct Beams {
+    x: HashMap<i64, usize>,
+    y: i64,
+}
+
+impl Beams {
+    fn solve(mut self, manifold: &Grid<char>) -> (usize, usize) {
+        let mut num_splits = 0;
+        while self.y + 1 < manifold.num_rows() as i64 {
+            self.x = self
+                .x
+                .into_iter()
+                .flat_map(|(x, count)| {
+                    if manifold.get((x, self.y + 1)).unwrap() == &'^' {
+                        num_splits += 1;
+                        Two((x + 1, count), (x - 1, count))
+                    } else {
+                        One((x, count))
+                    }
+                })
+                .fold(HashMap::new(), |mut map, (x, count)| {
+                    *map.entry(x).or_insert(0) += count;
+                    map
+                });
+            self.y += 1;
+        }
+        (num_splits, self.x.values().sum())
+    }
+}
+
+#[aoc_main]
+fn solve(input: Input) -> impl Into<Solution> {
+    let manifold = input.char_grid();
+    let start = manifold.find_position(&'S').unwrap();
+
+    Beams { x: HashMap::from([(start.x, 1)]), y: start.y }.solve(&manifold)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_examples() {
+        use utils::assert_example;
+        assert_example!(
+            r#".......S.......
+...............
+.......^.......
+...............
+......^.^......
+...............
+.....^.^.^.....
+...............
+....^.^...^....
+...............
+...^.^...^.^...
+...............
+..^...^.....^..
+...............
+.^.^.^.^.^...^.
+..............."#,
+            21,
+            40
+        );
+    }
+}