feat: Day 4

.gitignore

@@ -1,3 +1,4 @@
 */target/
 */input/
 *.out
+.direnv

aoc_2025/Cargo.lock

@@ -0,0 +1,149 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "allocator-api2"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "683d7910e743518b0e34f1186f92494becacb047c7b6bf616c96772180fef923"
+
+[[package]]
+name = "aoc_2025"
+version = "0.1.0"
+dependencies = [
+ "hashbrown",
+ "num",
+ "num-modular",
+ "topological-sort",
+ "winnow",
+]
+
+[[package]]
+name = "autocfg"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
+
+[[package]]
+name = "equivalent"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
+
+[[package]]
+name = "foldhash"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
+
+[[package]]
+name = "hashbrown"
+version = "0.16.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
+dependencies = [
+ "allocator-api2",
+ "equivalent",
+ "foldhash",
+]
+
+[[package]]
+name = "memchr"
+version = "2.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f52b00d39961fc5b2736ea853c9cc86238e165017a493d1d5c8eac6bdc4cc273"
+
+[[package]]
+name = "num"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "35bd024e8b2ff75562e5f34e7f4905839deb4b22955ef5e73d2fea1b9813cb23"
+dependencies = [
+ "num-bigint",
+ "num-complex",
+ "num-integer",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+]
+
+[[package]]
+name = "num-bigint"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5e44f723f1133c9deac646763579fdb3ac745e418f2a7af9cd0c431da1f20b9"
+dependencies = [
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-complex"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73f88a1307638156682bada9d7604135552957b7818057dcef22705b4d509495"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.46"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7969661fd2958a5cb096e56c8e1ad0444ac2bbcd0061bd28660485a44879858f"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-iter"
+version = "0.1.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1429034a0490724d0075ebb2bc9e875d6503c3cf69e235a8941aa757d83ef5bf"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-modular"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "17bb261bf36fa7d83f4c294f834e91256769097b3cb505d44831e0a179ac647f"
+
+[[package]]
+name = "num-rational"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f83d14da390562dca69fc84082e73e548e1ad308d24accdedd2720017cb37824"
+dependencies = [
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "topological-sort"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea68304e134ecd095ac6c3574494fc62b909f416c4fca77e440530221e549d3d"
+
+[[package]]
+name = "winnow"
+version = "0.7.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a5364e9d77fcdeeaa6062ced926ee3381faa2ee02d3eb83a5c27a8825540829"
+dependencies = [
+ "memchr",
+]

aoc_2025/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "aoc_2025"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+hashbrown = "0.16.1"
+num = "0.4.3"
+num-modular = "0.6.1"
+topological-sort = "0.2.2"
+winnow = "0.7.14"

aoc_2025/README.md

@@ -0,0 +1,3 @@
+```bash
+bacon test -- dayN
+```

aoc_2025/src/day1.rs

@@ -0,0 +1,124 @@
+use crate::{AoC, WinnowDay};
+use winnow::{
+    Parser, Result,
+    ascii::{digit1, multispace0},
+    combinator::{alt, preceded, repeat},
+};
+
+type Parsed = Vec<Side>;
+enum Side {
+    Left(i64),
+    Right(i64),
+}
+
+fn day() -> impl WinnowDay {
+    AoC::new(parse as _, part1 as _, part2 as _)
+}
+
+fn parse(input: &mut &str) -> Result<Parsed> {
+    repeat(1.., parse_line).parse_next(input)
+}
+
+fn parse_line(input: &mut &str) -> Result<Side> {
+    preceded(multispace0, alt((parse_left, parse_right))).parse_next(input)
+}
+
+fn parse_left(input: &mut &str) -> Result<Side> {
+    preceded("L", digit1.parse_to())
+        .map(Side::Left)
+        .parse_next(input)
+}
+
+fn parse_right(input: &mut &str) -> Result<Side> {
+    preceded("R", digit1.parse_to())
+        .map(Side::Right)
+        .parse_next(input)
+}
+
+fn part1(input: Parsed) -> String {
+    let mut res = 0;
+    let mut pos = 50i64;
+    for change in input {
+        match change {
+            Side::Left(dx) => pos = (pos + 100 - dx) % 100,
+            Side::Right(dx) => pos = (pos + dx) % 100,
+        }
+        if pos == 0 {
+            res += 1
+        }
+    }
+    format!("{res}")
+}
+
+fn part2(input: Parsed) -> String {
+    let input = input
+        .iter()
+        .flat_map(|side| match side {
+            Side::Left(dx) => (0..*dx).map(|_| Side::Left(1)).collect::<Vec<Side>>(),
+            Side::Right(dx) => (0..*dx).map(|_| Side::Right(1)).collect::<Vec<Side>>(),
+        })
+        .collect::<Vec<Side>>();
+    let mut res = 0;
+    let mut pos = 50i64;
+    for change in input {
+        match change {
+            Side::Left(dx) => pos = (pos + 100 - dx) % 100,
+            Side::Right(dx) => pos = (pos + dx) % 100,
+        }
+        if pos == 0 {
+            res += 1
+        }
+    }
+    format!("{res}")
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Day;
+
+    use super::*;
+
+    #[test]
+    fn part1_test() {
+        day().assert1(
+            "L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82",
+            "3",
+        );
+    }
+
+    #[test]
+    fn part1_solve() {
+        day().assert1(include_str!("../input/day1.txt"), "982");
+    }
+
+    #[test]
+    fn part2_test() {
+        day().assert2(
+            "L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82",
+            "6",
+        );
+    }
+
+    #[test]
+    fn part2_solve() {
+        day().assert2(include_str!("../input/day1.txt"), "6106");
+    }
+}

aoc_2025/src/day2.rs

@@ -0,0 +1,87 @@
+use crate::{AoC, WinnowDay};
+use winnow::{
+    Parser, Result,
+    ascii::digit1,
+    combinator::{separated, separated_pair},
+};
+
+type Parsed = Vec<(u64, u64)>;
+
+fn day() -> impl WinnowDay {
+    AoC::new(parse as _, part1 as _, part2 as _)
+}
+
+fn parse(input: &mut &str) -> Result<Parsed> {
+    separated(1.., parse_range, ",").parse_next(input)
+}
+
+fn parse_range(input: &mut &str) -> Result<(u64, u64)> {
+    separated_pair(digit1.parse_to(), "-", digit1.parse_to()).parse_next(input)
+}
+
+fn part1(input: Parsed) -> String {
+    let res = input
+        .iter()
+        .map(|(from, to)| {
+            (*from..=*to)
+                .filter(|i| {
+                    let n = (i.ilog10() + 1) >> 1;
+                    let p = 10u64.pow(n);
+                    i / p == i % p
+                })
+                .sum::<u64>()
+        })
+        .sum::<u64>();
+    format!("{res}")
+}
+
+fn part2(input: Parsed) -> String {
+    let res = input
+        .iter()
+        .map(|(from, to)| {
+            (*from..=*to)
+                .filter(|i| {
+                    let n = i.ilog10() + 1;
+                    (1..=(n >> 1)).filter(|p| n % p == 0).any(|p| {
+                        (1..(n / p))
+                            .all(|s| i % 10u64.pow(p) == (i / 10u64.pow(p * s)) % 10u64.pow(p))
+                    })
+                })
+                .sum::<u64>()
+        })
+        .sum::<u64>();
+    format!("{res}")
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Day;
+
+    use super::*;
+
+    #[test]
+    fn part1_test() {
+        day().assert1(
+            "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124",
+            "1227775554",
+        );
+    }
+
+    #[test]
+    fn part1_solve() {
+        day().assert1(include_str!("../input/day2.txt"), "12599655151");
+    }
+
+    #[test]
+    fn part2_test() {
+        day().assert2(
+            "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124",
+            "4174379265",
+        );
+    }
+
+    #[test]
+    fn part2_solve() {
+        day().assert2(include_str!("../input/day2.txt"), "20942028255");
+    }
+}

aoc_2025/src/day3.rs

@@ -0,0 +1,102 @@
+use std::iter::Sum;
+
+use crate::{AoC, WinnowDay};
+use winnow::{
+    Parser, Result,
+    ascii::newline,
+    combinator::{repeat, terminated},
+    error::ContextError,
+    token::one_of,
+};
+
+fn day() -> impl WinnowDay {
+    AoC::new(parse as _, part1 as _, part2 as _)
+}
+
+fn parse(input: &mut &str) -> Result<Vec<Vec<usize>>> {
+    repeat(1.., parse_line).parse_next(input)
+}
+
+fn parse_line(input: &mut &str) -> Result<Vec<usize>, ContextError> {
+    terminated(
+        repeat(
+            1..,
+            one_of(('0'..='9',)).map(|c: char| c.to_string().parse::<usize>().unwrap()),
+        ),
+        newline,
+    )
+    .parse_next(input)
+}
+
+fn part1(input: Vec<Vec<usize>>) -> usize {
+    input.iter().map(joltage(2)).sum()
+}
+
+fn part2(input: Vec<Vec<usize>>) -> usize {
+    input.iter().map(joltage(12)).sum()
+}
+
+fn joltage<
+    'a,
+    B: IntoIterator<IntoIter = I> + Copy,
+    I: ExactSizeIterator<Item = &'a N>,
+    N: Sum<&'a N> + Into<usize> + From<usize> + Copy + Default + 'a,
+>(
+    size: usize,
+) -> impl Fn(B) -> N {
+    move |line| {
+        (line.into_iter().len() - size..line.into_iter().len())
+            .fold((0, 0), |(start, val), end| {
+                line.into_iter()
+                    .enumerate()
+                    .skip(start)
+                    .take(end - start + 1)
+                    .map(|(i, v)| (i + 1, (*v).into() + val * 10))
+                    .reduce(|a, b| if a.1 >= b.1 { a } else { b })
+                    .unwrap()
+            })
+            .1
+            .into()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Day;
+
+    use super::*;
+
+    #[test]
+    fn part1_test() {
+        day().assert1(
+            "987654321111111
+811111111111119
+234234234234278
+818181911112111
+",
+            "357",
+        );
+    }
+
+    #[test]
+    fn part1_solve() {
+        day().assert1(include_str!("../input/day3.txt"), "17343");
+    }
+
+    #[test]
+    fn part2_test() {
+        day().assert2(
+            "987654321111111
+811111111111119
+234234234234278
+818181911112111
+",
+            "3121910778619",
+        );
+    }
+
+    #[test]
+    fn part2_solve() {
+        day().assert2(include_str!("../input/day3.txt"), "172664333119298");
+    }
+}

aoc_2025/src/day4.rs

@@ -0,0 +1,155 @@
+use winnow::{
+    Parser, Result,
+    ascii::{multispace0, newline},
+    combinator::{alt, preceded, repeat, terminated},
+};
+
+use crate::{AoC, SimpleDay, WinnowDay};
+
+fn day() -> impl WinnowDay {
+    AoC::new(parse as _, part1 as _, part2 as _)
+}
+
+type Parsed = Vec<Vec<Cell>>;
+
+#[derive(Debug, PartialEq, Eq)]
+enum Cell {
+    Empty,
+    Paper,
+}
+
+impl Cell {
+    fn is_empty(&self) -> bool {
+        self == &Cell::Empty
+    }
+
+    fn is_paper(&self) -> bool {
+        self == &Cell::Paper
+    }
+}
+
+fn parse(input: &mut &str) -> Result<Parsed> {
+    repeat(1.., preceded(multispace0, parse_line)).parse_next(input)
+}
+
+fn parse_line(input: &mut &str) -> Result<Vec<Cell>> {
+    repeat(1.., parse_cell).parse_next(input)
+}
+
+fn parse_cell(input: &mut &str) -> Result<Cell> {
+    alt((".".map(|_| Cell::Empty), "@".map(|_| Cell::Paper))).parse_next(input)
+}
+
+fn part1(input: Parsed) -> usize {
+    let mut input = input;
+    remove_paper(&mut input)
+}
+
+fn remove_paper(input: &mut [Vec<Cell>]) -> usize {
+    let mut score = 0;
+    let mut access = Vec::new();
+    let h = input.len();
+    let w = input[0].len();
+    let directions = [
+        (-1, -1),
+        (0, -1),
+        (1, -1),
+        (1, 0),
+        (1, 1),
+        (0, 1),
+        (-1, 1),
+        (-1, 0),
+    ];
+    for y in 0..h {
+        for x in 0..w {
+            match input[y][x] {
+                Cell::Empty => {}
+                Cell::Paper => {
+                    let count = directions
+                        .iter()
+                        .filter(|dir| {
+                            let nx = x as isize + dir.0;
+                            let ny = y as isize + dir.1;
+                            nx >= 0
+                                && nx < w as isize
+                                && ny >= 0
+                                && ny < h as isize
+                                && input[ny as usize][nx as usize].is_paper()
+                        })
+                        .count();
+                    if count < 4 {
+                        score += 1;
+                        access.push((x, y));
+                    }
+                }
+            }
+        }
+    }
+    access.iter().for_each(|(x, y)| {
+        input[*y][*x] = Cell::Empty;
+    });
+    score
+}
+
+fn part2(input: Parsed) -> usize {
+    let mut input = input;
+    let mut score = 0;
+    loop {
+        let removed = remove_paper(&mut input);
+        score += removed;
+        if removed == 0 {
+            return score;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Day;
+
+    use super::*;
+
+    #[test]
+    fn part1_test() {
+        day().assert1(
+            "..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.",
+            "13",
+        );
+    }
+
+    #[test]
+    fn part1_solve() {
+        day().assert1(include_str!("../input/day4.txt"), "1356");
+    }
+
+    #[test]
+    fn part2_test() {
+        day().assert2(
+            "..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.",
+            "43",
+        );
+    }
+
+    #[test]
+    fn part2_solve() {
+        day().assert2(include_str!("../input/day4.txt"), "8713");
+    }
+}

aoc_2025/src/lib.rs

@@ -0,0 +1,99 @@
+#![allow(dead_code)]
+#![allow(unused)]
+
+use std::fmt::{Debug, Display};
+
+use winnow::Parser;
+
+mod day1;
+mod day2;
+mod day3;
+mod day4;
+
+trait Day {
+    fn assert1(&self, input: &str, output: &str);
+    fn assert2(&self, input: &str, output: &str);
+}
+
+struct AoC<P, O1, O2> {
+    parse: P,
+    part1: O1,
+    part2: O2,
+}
+
+impl<P, O1, O2> AoC<P, O1, O2> {
+    fn new(parse: P, part1: O1, part2: O2) -> Self {
+        Self {
+            parse,
+            part1,
+            part2,
+        }
+    }
+}
+
+trait SimpleDay: Day {}
+
+impl<P, O1, O2> SimpleDay for AoC<fn(String) -> P, fn(P) -> O1, fn(P) -> O2>
+where
+    O1: Display,
+    O2: Display,
+{
+}
+
+impl<P, O1, O2> Day for AoC<fn(String) -> P, fn(P) -> O1, fn(P) -> O2>
+where
+    O1: Display,
+    O2: Display,
+{
+    fn assert1(&self, input: &str, output: &str) {
+        let parsed = (self.parse)(input.to_string());
+        assert_eq!(format!("{}", (self.part1)(parsed)), output);
+    }
+
+    fn assert2(&self, input: &str, output: &str) {
+        let parsed = (self.parse)(input.to_string());
+        assert_eq!(format!("{}", (self.part2)(parsed)), output);
+    }
+}
+
+trait WinnowDay: Day {}
+
+impl<O, E, O1, O2> WinnowDay
+    for AoC<for<'a, 'b> fn(&'a mut &'b str) -> Result<O, E>, fn(O) -> O1, fn(O) -> O2>
+where
+    E: Debug,
+    O1: Display,
+    O2: Display,
+{
+}
+
+fn as_parser<O, E>(
+    func: for<'a, 'b> fn(&'a mut &'b str) -> Result<O, E>,
+) -> impl for<'a> Parser<&'a str, O, E>
+where
+    E: Debug,
+{
+    func
+}
+
+impl<O, E, O1, O2> Day
+    for AoC<for<'a, 'b> fn(&'a mut &'b str) -> Result<O, E>, fn(O) -> O1, fn(O) -> O2>
+where
+    E: Debug,
+    O1: Display,
+    O2: Display,
+{
+    fn assert1(&self, input: &str, output: &str) {
+        let mut input = input;
+        let mut parser = as_parser(self.parse);
+        let parsed = parser.parse_next(&mut input).unwrap();
+        assert_eq!(format!("{}", (self.part1)(parsed)), output);
+    }
+
+    fn assert2(&self, input: &str, output: &str) {
+        let mut input = input;
+        let mut parser = as_parser(self.parse);
+        let parsed = parser.parse_next(&mut input).unwrap();
+        assert_eq!(format!("{}", (self.part2)(parsed)), output);
+    }
+}

aoc_2025/src/template.rs

@@ -0,0 +1,48 @@
+use winnow::{Parser, Result};
+
+use crate::{AoC, SimpleDay, WinnowDay};
+
+fn day() -> impl WinnowDay {
+    AoC::new(parse as _, part1 as _, part2 as _)
+}
+
+type Parsed = ();
+
+fn parse(input: &mut &str) -> Result<Parsed> {
+    "".map(|_| ()).parse_next(input)
+}
+
+fn part1(input: Parsed) -> usize {
+    0
+}
+
+fn part2(input: Parsed) -> usize {
+    0
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Day;
+
+    use super::*;
+
+    #[test]
+    fn part1_test() {
+        day().assert1("", "");
+    }
+
+    #[test]
+    fn part1_solve() {
+        day().assert1(include_str!("../input/day.txt"), "");
+    }
+
+    // #[test]
+    // fn part2_test() {
+    //     day().assert2("", "");
+    // }
+
+    // #[test]
+    // fn part2_solve() {
+    //     day().assert2(include_str!("../input/day.txt"), "");
+    // }
+}

flake.lock

@@ -0,0 +1,61 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1764242076,
+        "narHash": "sha256-sKoIWfnijJ0+9e4wRvIgm/HgE27bzwQxcEmo2J/gNpI=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "2fad6eac6077f03fe109c4d4eb171cf96791faa4",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,32 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs =
+    {
+      nixpkgs,
+      flake-utils,
+      ...
+    }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            cargo
+            rustc
+            rustfmt
+            clippy
+            bacon
+          ];
+        };
+      }
+    );
+}