some sort of infinite loop...

Author: tom-anders

Cargo.toml

@@ -2,7 +2,7 @@
 resolver = "2"
 members = [
     "utils",
-    "aoc_derive", "day1", "day2", "day3", "day4", "day5", "day6", "day7", "day8", "day9", "day10", "day11",
+    "aoc_derive", "day1", "day2", "day3", "day4", "day5", "day6", "day7", "day8", "day9", "day10", "day11", "day12",
 ]
 
 [workspace.dependencies]

day12/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "day12"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+aoc_derive.path = '../aoc_derive'
+utils.path = '../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

day12/src/main.rs

@@ -0,0 +1,107 @@
+use std::collections::HashSet;
+
+use aoc_derive::aoc_main;
+use graphs::floodfill;
+use itertools::Itertools;
+use lazy_regex::regex;
+use math::Vec2D;
+use utils::ParseInput;
+use utils::*;
+
+#[aoc_main]
+fn solve(input: Input) -> impl Into<Solution> {
+    let mut regions = Vec::<(char, HashSet<Vec2D>)>::new();
+
+    let map = input.char_grid();
+
+    let mut visited = HashSet::new();
+    for (pos, &c) in map.iter() {
+        if !visited.contains(&pos) {
+            println!("new region {c}");
+
+            let mut new_region = HashSet::new();
+            let mut next = vec![pos];
+            loop {
+                for p in &next {
+                    new_region.insert(*p);
+                }
+
+                next = next
+                    .into_iter()
+                    .flat_map(|n| {
+                        map.orthogonal_neighbors(&n)
+                            .filter(|neighb| map[*neighb] == c && !new_region.contains(neighb))
+                            .collect_vec()
+                            .into_iter()
+                    })
+                    .collect();
+
+                if next.is_empty() {
+                    break;
+                }
+
+                dbg!(next.len());
+            }
+
+            visited.extend(new_region.clone());
+
+            regions.push((c, new_region));
+        }
+    }
+
+    let part1 = regions
+        .iter()
+        .map(|(c, region)| {
+            let area = region.len();
+            let perimeter = region
+                .iter()
+                .map(|pos| pos.orthogonal_neighbors().filter(|n| map.get(*n) != Some(c)).count())
+                .sum_usize();
+
+            //println!("Region {c} has area {area} and perimeter {perimeter}");
+
+            area * perimeter
+        })
+        .sum_usize();
+
+    (part1)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_examples() {
+        use utils::assert_example;
+        assert_example!(
+            r#"AAAA
+BBCD
+BBCC
+EEEC"#,
+            "140"
+        );
+
+        assert_example!(
+            "OOOOO
+OXOXO
+OOOOO
+OXOXO
+OOOOO",
+            772
+        );
+
+        assert_example!(
+            "RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE",
+            1930
+        );
+    }
+}