add day12

Author: mirsella

2024/day12/.gitignore

@@ -0,0 +1,19 @@
+input.txt
+flamegraph.svg
+perf.data*
+### Rust
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+

2024/day12/Cargo.toml

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+[package]
+name = "day12"
+authors = ["mirsella <[email protected]>"]
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+regex = { workspace = true }
+itertools = { workspace = true }
+pathfinding = { workspace = true }
+rayon = { workspace = true }
+indexmap = { workspace = true }
+hashbrown = { workspace = true }
+fix_fn = { workspace = true }

2024/day12/src/main.rs

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+use hashbrown::HashSet;
+use itertools::Itertools;
+use std::collections::BTreeSet;
+// use std::collections::HashSet;
+use pathfinding::{
+    matrix::{directions::DIRECTIONS_4, Matrix},
+    prelude::bfs_reach,
+};
+
+type Regions = HashSet<BTreeSet<(usize, usize)>>;
+fn part1(input: &str) -> usize {
+    let m = Matrix::from_rows(input.lines().map(str::chars)).unwrap();
+    let mut regions: Regions = Default::default();
+    for pos in m.keys() {
+        if regions.iter().any(|r| r.contains(&pos)) {
+            continue;
+        }
+        let region = bfs_reach(pos, |&p| m.neighbours(p, false).filter(|&n| m[n] == m[pos]))
+            .collect::<BTreeSet<_>>();
+        regions.insert(region);
+    }
+    let mut price = 0;
+    for region in regions.iter() {
+        let mut fences = 0;
+        for &pos in region {
+            let neighbours = m.neighbours(pos, false).collect_vec();
+            fences += neighbours.iter().filter(|n| !region.contains(n)).count();
+            fences += 4 - neighbours.len();
+        }
+        price += fences * region.len();
+    }
+    price
+}
+
+fn part2(input: &str) -> usize {
+    let m = Matrix::from_rows(input.lines().map(str::chars)).unwrap();
+    let mut regions: Regions = Default::default();
+    for pos in m.keys() {
+        if regions.iter().any(|r| r.contains(&pos)) {
+            continue;
+        }
+        let region = bfs_reach(pos, |&p| m.neighbours(p, false).filter(|&n| m[n] == m[pos]))
+            .collect::<BTreeSet<_>>();
+        regions.insert(region);
+    }
+    let mut price = 0;
+    for region in regions.iter() {
+        let mut corners = 0;
+        for dir in DIRECTIONS_4 {
+            let mut sides = HashSet::new();
+            for pos in region {
+                let tmp = (pos.0 as isize + dir.0, pos.1 as isize + dir.1);
+                if !region.contains(&(tmp.0 as usize, tmp.1 as usize)) {
+                    sides.insert(tmp);
+                }
+            }
+            let mut extra_sides = HashSet::new();
+            for side in &sides {
+                let mut tmp = (side.0 + dir.1, side.1 + dir.0);
+                while sides.contains(&tmp) {
+                    extra_sides.insert(tmp);
+                    tmp = (tmp.0 + dir.1, tmp.1 + dir.0);
+                }
+            }
+            corners += sides.len() - extra_sides.len();
+        }
+        price += corners * region.len();
+    }
+    price
+}
+
+fn main() {
+    let input = include_str!("../input.txt");
+    println!("Part 1: {}", part1(input));
+    println!("Part 2: {}", part2(input));
+}
+
+#[cfg(test)]
+mod tests {
+    const INPUT: &str = "RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE";
+    #[test]
+    fn part1() {
+        assert_eq!(super::part1(INPUT), 1930);
+    }
+    #[test]
+    fn part2() {
+        assert_eq!(super::part2(INPUT), 1206);
+    }
+    #[test]
+    fn part2_2() {
+        assert_eq!(
+            super::part2(
+                "AAAA
+BBCD
+BBCC
+EEEC"
+            ),
+            80
+        );
+    }
+    #[test]
+    fn part2_3() {
+        assert_eq!(
+            super::part2(
+                "EEEEE
+EXXXX
+EEEEE
+EXXXX
+EEEEE"
+            ),
+            236
+        );
+    }
+
+    #[test]
+    fn part2_4() {
+        assert_eq!(
+            super::part2(
+                "AAAAAA
+AAABBA
+AAABBA
+ABBAAA
+ABBAAA
+AAAAAA"
+            ),
+            368
+        );
+    }
+}