add day8

Author: mirsella

2024/day8/.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/day8/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "day8"
+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 }
+glam = { version = "0.29.2", features = ["debug-glam-assert"] }

2024/day8/src/main.rs

@@ -0,0 +1,100 @@
+use glam::Vec2;
+use pathfinding::matrix::Matrix;
+use std::collections::HashSet;
+
+fn part1(input: &str) -> usize {
+    let m = Matrix::from_rows(input.lines().map(str::chars)).unwrap();
+    let mut set = HashSet::new();
+    for (apos, c) in m.items() {
+        if *c == '.' {
+            continue;
+        }
+        for (bpos, cb) in m.items() {
+            if c != cb || apos == bpos {
+                continue;
+            }
+            let avec = Vec2::new(apos.1 as f32, apos.0 as f32);
+            let bvec = Vec2::new(bpos.1 as f32, bpos.0 as f32);
+            let anewvec = avec.lerp(bvec, 2.);
+            let bnewvec = bvec.lerp(avec, 2.);
+            let anew = (anewvec.y as usize, anewvec.x as usize);
+            let bnew = (bnewvec.y as usize, bnewvec.x as usize);
+            if anewvec.x >= 0. && anewvec.y >= 0. && m.within_bounds(anew) {
+                set.insert(anew);
+            }
+            if bnewvec.x >= 0. && bnewvec.y >= 0. && m.within_bounds(bnew) {
+                set.insert(bnew);
+            }
+        }
+    }
+    set.len()
+}
+fn part2(input: &str) -> usize {
+    let m = Matrix::from_rows(input.lines().map(str::chars)).unwrap();
+    let mut set = HashSet::new();
+    for (apos, c) in m.items() {
+        if *c == '.' {
+            continue;
+        }
+        for (bpos, cb) in m.items().skip(apos.0 + apos.1) {
+            if c != cb || apos == bpos {
+                continue;
+            }
+            let avec = Vec2::new(apos.1 as f32, apos.0 as f32);
+            let bvec = Vec2::new(bpos.1 as f32, bpos.0 as f32);
+            let mut factor = 1.;
+            loop {
+                let mut out = [false; 2];
+                let anewvec = avec + (bvec - avec) * factor;
+                let bnewvec = bvec + (avec - bvec) * factor;
+                let anew = (anewvec.y as usize, anewvec.x as usize);
+                let bnew = (bnewvec.y as usize, bnewvec.x as usize);
+                if anewvec.x >= 0. && anewvec.y >= 0. && m.within_bounds(anew) {
+                    set.insert(anew);
+                } else {
+                    out[0] = true;
+                }
+                if bnewvec.x >= 0. && bnewvec.y >= 0. && m.within_bounds(bnew) {
+                    set.insert(bnew);
+                } else {
+                    out[1] = true;
+                }
+                if out[0] && out[1] {
+                    break;
+                }
+                factor += 1.;
+            }
+        }
+    }
+    set.len()
+}
+
+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 = "............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............";
+    #[test]
+    fn part1() {
+        assert_eq!(super::part1(INPUT), 14);
+    }
+    #[test]
+    fn part2() {
+        assert_eq!(super::part2(INPUT), 34);
+    }
+}