Solve day 6

Weirdly improves speed of part1 but hurts speed of part2 🤷

.cargo/config.toml

@@ -0,0 +1,2 @@
+[build]
+rustflags = ["-C", "target-cpu=native", "-Cforce-frame-pointers=yes"]

Cargo.toml

@@ -4,14 +4,38 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+clap = { version = "4.5", features = ["derive"] }
 color-eyre = "0.6"
-tracing = "0.1"
+itertools = "0.14"
+rayon = "1.11"
+tracing = { version = "0.1", features = ["release_max_level_info"] }
 tracing-error = "0.2"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 
 [dev-dependencies]
-test-log = {version = "0.2", default-features = false, features = ["trace"]}
+criterion = "0.5"
+pprof = { version = "0.15" , features = ["flamegraph", "criterion"] }
+test-log = { version = "0.2", default-features = false, features = ["trace"] }
 
 # Improve perf on debug builds: https://docs.rs/color-eyre/latest/color_eyre/#improving-perf-on-debug-builds
 [profile.dev.package.backtrace]
 opt-level = 3
+
+# Gotta go fast
+[profile.release]
+codegen-units = 1
+lto = "fat"
+panic = "abort"
+debug = false # set true for profiling
+
+[lib]
+name = "aoc"
+path = "src/lib.rs"
+
+[[bin]]
+name = "aoc_bin"
+path = "src/main.rs"
+
+[[bench]]
+name = "aoc"
+harness = false

README.md

@@ -1,15 +1,50 @@
 # Advent of Code 2025
 
-Rusty edition.
+Rusty and over-engineered edition.
 
 ## Running
 
 By request of AoC creator, I haven't included the input files (e.g. src/input/day01.txt). Log into the Advent of Code site and save the inputs there to the src/input/ folder.
 
-Then to run: `cargo run`.
+To run all days: `cargo run`.
+
+To run a specific day and/or part: `cargo run -- --day 1 --part 1`.
 
 To run in super-fast prod mode: `cargo run --release`.
 
 To run with debug logs enabled: `RUST_LOG=debug cargo run`.
 
-To run the tests against included test input files: `RUST_LOG=debug cargo test -- --no-capture`.
+To run all the tests against included test input files: `RUST_LOG=debug cargo test -- --no-capture`.
+
+To run the tests for a specific day and/or part: `RUST_LOG=debug cargo test day01::test::test_part1 -- --no-capture`.
+
+## Benchmarks
+
+Because this is over-engineered, I've included benchmarks for each day's solution. Because, why not?
+
+To run benchmarks: `cargo bench`. Or a specific day and/or part: `cargo bench -- "day02 part1"`.
+
+### Results
+
+These were all run on my personal machine, an AMD Ryzen 9 3900X 12-Core Processor with 32 GB RAM, on Linux (WSL), with nightly rust.
+
+Timings are given as: [lower-bound **best-estimate** upper-bound]
+
+| Day | Part 1 | Part 2 |
+|-----|--------|--------|
+| 01  | [79.998 µs **80.349 µs** 80.721 µs] | [76.289 µs **76.616 µs** 76.950 µs] |
+| 02  | [2.0386 ms **2.0483 ms** 2.0584 ms] | [2.0823 ms **2.0918 ms** 2.1015 ms] |
+| 03  | [45.711 µs **45.937 µs** 46.177 µs] | [267.18 µs **267.95 µs** 268.75 µs] |
+| 04  | [143.40 µs **144.00 µs** 144.73 µs] | [1.6165 ms **1.6258 ms** 1.6355 ms] |
+| 05  | [187.25 µs **188.93 µs** 190.74 µs] | [63.809 µs **64.204 µs** 64.606 µs] |
+| 06  | [128.44 µs **129.44 µs** 130.52 µs] | [165.05 µs **165.70 µs** 166.36 µs] |
+
+## Profiling
+
+To aid in increasing performance, the `pprof` crate can be used to generate flamegraphs off of the benchmarks.
+
+To run profiling across all benchmarks: `cargo bench --bench aoc -- --profile-time 10`.
+
+To run profile the benchmark for a specific day and/or part: `cargo bench --bench aoc -- --profile-time 30 "day01 part1"`.
+
+The flamegraphs will be generated in `target/criterion/<benchmark_name>/profile/flamegraph.svg`.

benches/aoc.rs

@@ -0,0 +1,36 @@
+use criterion::{Criterion, criterion_group, criterion_main};
+use pprof::criterion::{Output, PProfProfiler};
+
+const PPROF_SAMPLING_FREQ_HZ: i32 = 997;
+
+macro_rules! bench_days {
+    ($($day_num:literal => $day_mod:ident),* $(,)?) => {
+        $(
+            mod $day_mod {
+                use super::*;
+                use aoc::$day_mod;
+
+                pub fn part1(c: &mut Criterion) {
+                    c.bench_function(concat!(stringify!($day_mod), " part1"), |b| {
+                        b.iter(|| $day_mod::part1($day_mod::INPUT))
+                    });
+                }
+
+                pub fn part2(c: &mut Criterion) {
+                    c.bench_function(concat!(stringify!($day_mod), " part2"), |b| {
+                        b.iter(|| $day_mod::part2($day_mod::INPUT))
+                    });
+                }
+            }
+        )*
+
+        criterion_group! {
+            name = benches;
+            config = Criterion::default().with_profiler(PProfProfiler::new(PPROF_SAMPLING_FREQ_HZ, Output::Flamegraph(None)));
+            targets = $($day_mod::part1, $day_mod::part2),*
+        }
+        criterion_main!(benches);
+    };
+}
+
+aoc::all_days!(bench_days);

src/day01/mod.rs

@@ -4,9 +4,9 @@ use color_eyre::{
     Result,
     eyre::{Error, eyre},
 };
-use tracing::{debug, info, instrument};
+use tracing::{debug, instrument};
 
-const INPUT: &str = include_str!("input/input.txt");
+pub const INPUT: &str = include_str!("input/input.txt");
 
 const LOCK_SIZE: i32 = 100;
 const LOCK_STARTING_POSITION: i32 = 50;
@@ -30,7 +30,7 @@ impl FromStr for Direction {
 }
 
 #[instrument(skip(input))]
-fn part1(input: &str) -> Result<i32> {
+pub fn part1(input: &str) -> Result<i32> {
     let mut dial = LOCK_STARTING_POSITION;
     let mut visited_zero_count = 0;
     for line in input.trim().split('\n') {
@@ -57,7 +57,7 @@ fn part1(input: &str) -> Result<i32> {
 }
 
 #[instrument(skip(input))]
-fn part2(input: &str) -> Result<i32> {
+pub fn part2(input: &str) -> Result<i32> {
     let mut dial = LOCK_STARTING_POSITION;
     let mut visited_zero_count = 0;
     for line in input.trim().split('\n') {
@@ -98,18 +98,6 @@ fn part2(input: &str) -> Result<i32> {
     Ok(visited_zero_count)
 }
 
-pub fn solve() -> Result<()> {
-    info!("Day 1");
-    {
-        let _span = tracing::info_span!("day01").entered();
-        let p1 = part1(INPUT)?;
-        info!("Part 1: {}", p1);
-        let p2 = part2(INPUT)?;
-        info!("Part 2: {}", p2);
-    }
-    Ok(())
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

src/day02/input/test1.txt

@@ -0,0 +1 @@
+11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124

src/day02/mod.rs

@@ -0,0 +1,185 @@
+use std::{fmt::Display, str::FromStr};
+
+use color_eyre::{
+    Result,
+    eyre::{Error, eyre},
+};
+use rayon::prelude::*;
+use tracing::{debug, debug_span, instrument};
+
+pub const INPUT: &str = include_str!("input/input.txt");
+
+#[derive(Clone, Debug)]
+struct ProductRange(std::ops::RangeInclusive<i64>);
+
+impl FromStr for ProductRange {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut parts = s.split('-');
+        let start = parts
+            .next()
+            .ok_or(eyre!("Invalid product range: no start"))?
+            .parse::<i64>()?;
+        let end = parts
+            .next()
+            .ok_or(eyre!("Invalid product range: no end"))?
+            .parse::<i64>()?;
+        if parts.next().is_some() {
+            return Err(eyre!("Invalid product range: too many parts"));
+        }
+        Ok(ProductRange(start..=end))
+    }
+}
+
+impl Display for ProductRange {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}-{}", self.0.start(), self.0.end())
+    }
+}
+
+impl Iterator for ProductRange {
+    type Item = i64;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
+    }
+}
+
+impl ProductRange {
+    fn invalid_ids(self) -> Result<Vec<i64>> {
+        let start = *self.0.start();
+        let end = *self.0.end();
+
+        let mut invalid_ids = Vec::new();
+
+        // Determine digit ranges we need to check
+        let start_digits = if start == 0 { 1 } else { start.ilog10() + 1 };
+        let end_digits = if end == 0 { 1 } else { end.ilog10() + 1 };
+
+        for num_digits in start_digits..=end_digits {
+            // Skip odd digit counts - they're all valid
+            if num_digits % 2 != 0 {
+                continue;
+            }
+
+            let half_digits = num_digits / 2;
+            let half_min = 10_i64.pow(half_digits - 1);
+            let half_max = 10_i64.pow(half_digits) - 1;
+            let multiplier = 10_i64.pow(half_digits) + 1; // Pre-calculate: half * multiplier = AABB pattern
+
+            // Generate all patterns where first half == second half
+            for half in half_min..=half_max {
+                let id = half * multiplier;
+                if id >= start && id <= end {
+                    invalid_ids.push(id);
+                }
+            }
+        }
+
+        debug!("Invalid IDs: {:?}", &invalid_ids);
+        Ok(invalid_ids)
+    }
+
+    fn invalid_ids2(self) -> Result<Vec<i64>> {
+        let start = *self.0.start();
+        let end = *self.0.end();
+
+        let mut invalid_ids = std::collections::HashSet::new();
+
+        // Determine digit ranges we need to check
+        let start_digits = if start == 0 { 1 } else { start.ilog10() + 1 };
+        let end_digits = if end == 0 { 1 } else { end.ilog10() + 1 };
+
+        for num_digits in start_digits..=end_digits {
+            // Try all possible chunk sizes that divide evenly
+            for chunk_size in 1..=num_digits / 2 {
+                if num_digits % chunk_size != 0 {
+                    continue;
+                }
+
+                let num_chunks = num_digits / chunk_size;
+                if num_chunks < 2 {
+                    continue;
+                }
+
+                // Generate all possible chunk patterns
+                let chunk_min = 10_i64.pow(chunk_size - 1);
+                let chunk_max = 10_i64.pow(chunk_size) - 1;
+                let chunk_power = 10_i64.pow(chunk_size);
+
+                // Calculate multiplier for repeating pattern
+                // For ABCABC: chunk * (10^6 + 10^3 + 1) = chunk * 1001001
+                let mut multiplier = 0_i64;
+                for i in 0..num_chunks {
+                    multiplier += chunk_power.pow(i);
+                }
+
+                for chunk in chunk_min..=chunk_max {
+                    let id = chunk * multiplier;
+
+                    if id >= start && id <= end {
+                        invalid_ids.insert(id);
+                    }
+                }
+            }
+        }
+
+        let invalid_ids: Vec<i64> = invalid_ids.into_iter().collect();
+
+        debug!("Invalid IDs: {:?}", &invalid_ids);
+        Ok(invalid_ids)
+    }
+}
+
+#[instrument(skip(input))]
+pub fn part1(input: &str) -> Result<i64> {
+    input
+        .trim()
+        .split(',')
+        .collect::<Vec<_>>()
+        .into_par_iter()
+        .map(|range| {
+            let _span = debug_span!("range", range = %range).entered();
+            let range: ProductRange = range.parse()?;
+            Ok(range.invalid_ids()?.iter().sum::<i64>())
+        })
+        .sum()
+}
+
+#[instrument(skip(input))]
+pub fn part2(input: &str) -> Result<i64> {
+    input
+        .trim()
+        .split(',')
+        .collect::<Vec<_>>()
+        .into_par_iter()
+        .map(|range| {
+            let _span = debug_span!("range", range = %range).entered();
+            let range: ProductRange = range.parse()?;
+            Ok(range.invalid_ids2()?.iter().sum::<i64>())
+        })
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_log::test;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(TEST_INPUT1).unwrap(), 1227775554);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(TEST_INPUT1).unwrap(), 4174379265);
+    }
+}

src/day03/input/test1.txt

@@ -0,0 +1,4 @@
+987654321111111
+811111111111119
+234234234234278
+818181911112111

src/day03/mod.rs

@@ -0,0 +1,72 @@
+use color_eyre::Result;
+use tracing::{debug, instrument};
+
+pub const INPUT: &str = include_str!("input/input.txt");
+
+#[derive(Debug, Clone, Copy)]
+struct Battery {
+    column: usize,
+    joltage: u8,
+}
+
+impl Default for Battery {
+    fn default() -> Self {
+        Battery {
+            column: 0,
+            joltage: 0,
+        }
+    }
+}
+
+fn largest_output_joltage<const N: usize>(input: &str) -> Result<u64> {
+    let mut output_joltage: u64 = 0;
+    for line in input.trim().split('\n') {
+        let mut batteries: [Battery; N] = [Battery::default(); N];
+        let line_len = line.len();
+        for (column, joltage) in line.bytes().map(|c| c - b'0').enumerate() {
+            let min = N.saturating_sub(line_len - column);
+            for i in min..N {
+                if joltage > batteries[i].joltage {
+                    batteries[i].column = column;
+                    batteries[i].joltage = joltage;
+                    batteries[i + 1..].fill(Battery::default());
+                    break;
+                }
+            }
+        }
+        let line_joltage = batteries
+            .iter()
+            .fold(0u64, |acc, &b| acc * 10 + b.joltage as u64);
+        debug!(line, line_joltage);
+        output_joltage += line_joltage;
+    }
+    Ok(output_joltage)
+}
+
+#[instrument(skip(input))]
+pub fn part1(input: &str) -> Result<u64> {
+    largest_output_joltage::<2>(input)
+}
+
+#[instrument(skip(input))]
+pub fn part2(input: &str) -> Result<u64> {
+    largest_output_joltage::<12>(input)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_log::test;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(TEST_INPUT1).unwrap(), 357);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(TEST_INPUT1).unwrap(), 3121910778619);
+    }
+}

src/day04/input/test1.txt

@@ -0,0 +1,10 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.

src/day04/mod.rs

@@ -0,0 +1,172 @@
+use std::{
+    fmt::{Display, Formatter},
+    str::FromStr,
+};
+
+use color_eyre::{Result, eyre::eyre};
+use tracing::{debug, instrument};
+
+pub const INPUT: &str = include_str!("input/input.txt");
+
+const ADJACENT_DELTAS: [(isize, isize); 8] = [
+    (-1, -1),
+    (-1, 0),
+    (-1, 1),
+    (0, -1),
+    (0, 1),
+    (1, -1),
+    (1, 0),
+    (1, 1),
+];
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Cell {
+    Empty,
+    Paper,
+    AccessiblePaper,
+}
+
+impl FromStr for Cell {
+    type Err = color_eyre::Report;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "." => Ok(Cell::Empty),
+            "@" => Ok(Cell::Paper),
+            "x" => Ok(Cell::AccessiblePaper),
+            _ => Err(eyre!("Invalid cell character: {}", s)),
+        }
+    }
+}
+
+impl Cell {
+    fn from_byte(b: u8) -> Result<Self, color_eyre::Report> {
+        match b {
+            b'.' => Ok(Cell::Empty),
+            b'@' => Ok(Cell::Paper),
+            b'x' => Ok(Cell::AccessiblePaper),
+            _ => Err(eyre!("Invalid cell byte: {}", b)),
+        }
+    }
+}
+
+struct Grid<const R: usize, const C: usize> {
+    cells: [[Cell; C]; R],
+}
+
+impl<const R: usize, const C: usize> FromStr for Grid<R, C> {
+    type Err = color_eyre::Report;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut cells = [[Cell::Empty; C]; R];
+
+        for (row, line) in s.lines().enumerate() {
+            for (col, byte) in line.bytes().enumerate() {
+                cells[row][col] = Cell::from_byte(byte)?;
+            }
+        }
+
+        Ok(Grid { cells })
+    }
+}
+
+impl<const R: usize, const C: usize> Display for Grid<R, C> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        for row in 0..R {
+            for col in 0..C {
+                let symbol = match self.cells[row][col] {
+                    Cell::Empty => '.',
+                    Cell::Paper => '@',
+                    Cell::AccessiblePaper => 'x',
+                };
+                write!(f, "{}", symbol)?;
+            }
+            writeln!(f)?;
+        }
+        Ok(())
+    }
+}
+
+impl<const R: usize, const C: usize> Grid<R, C> {
+    fn count_accessible_papers(&mut self, replace_with: Cell) -> usize {
+        let mut count = 0;
+        for row in 0..R {
+            for col in 0..C {
+                if self.cells[row][col] != Cell::Paper {
+                    continue;
+                }
+                let mut adjacent_papers = 0;
+                for &(dr, dc) in &ADJACENT_DELTAS {
+                    let adj_row = row as isize + dr;
+                    let adj_col = col as isize + dc;
+                    if adj_row >= 0
+                        && adj_col >= 0
+                        && (adj_row as usize) < R
+                        && (adj_col as usize) < C
+                    {
+                        let adjacent = self.cells[adj_row as usize][adj_col as usize];
+                        if matches!(adjacent, Cell::Paper | Cell::AccessiblePaper) {
+                            adjacent_papers += 1;
+                        }
+                    }
+                }
+                if adjacent_papers < 4 {
+                    self.cells[row][col] = replace_with;
+                    count += 1;
+                }
+            }
+        }
+        count
+    }
+}
+
+fn solve_part1<const R: usize, const C: usize>(input: &str) -> Result<usize> {
+    let mut grid = Grid::<R, C>::from_str(input)?;
+    debug!("Parsed grid:\n{}", grid);
+    let count = grid.count_accessible_papers(Cell::AccessiblePaper);
+    debug!("Processed grid:\n{}", grid);
+    Ok(count)
+}
+
+#[instrument(skip(input))]
+pub fn part1(input: &str) -> Result<usize> {
+    solve_part1::<135, 135>(input)
+}
+
+fn solve_part2<const R: usize, const C: usize>(input: &str) -> Result<usize> {
+    let mut grid = Grid::<R, C>::from_str(input)?;
+    debug!("Parsed grid:\n{}", grid);
+    let mut count = 0;
+    loop {
+        let removed = grid.count_accessible_papers(Cell::Empty);
+        if removed == 0 {
+            break;
+        }
+        debug!("Removed {} in grid:\n{}", removed, grid);
+        count += removed;
+    }
+    Ok(count)
+}
+
+#[instrument(skip(input))]
+pub fn part2(input: &str) -> Result<usize> {
+    solve_part2::<135, 135>(input)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_log::test;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(solve_part1::<10, 10>(TEST_INPUT1).unwrap(), 13);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(solve_part2::<10, 10>(TEST_INPUT1).unwrap(), 43);
+    }
+}

src/day05/input/test1.txt

@@ -0,0 +1,11 @@
+3-5
+10-14
+16-20
+12-18
+
+1
+5
+8
+11
+17
+32

src/day05/mod.rs

@@ -0,0 +1,125 @@
+use std::{fmt::Display, str::FromStr};
+
+use color_eyre::{
+    Result,
+    eyre::{Error, eyre},
+};
+use tracing::{debug, instrument};
+
+pub const INPUT: &str = include_str!("input/input.txt");
+
+#[derive(Clone, Debug)]
+struct FreshRange(pub std::ops::RangeInclusive<i64>);
+
+impl FromStr for FreshRange {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut parts = s.split('-');
+        let start = parts
+            .next()
+            .ok_or(eyre!("Invalid fresh range: no start"))?
+            .parse::<i64>()?;
+        let end = parts
+            .next()
+            .ok_or(eyre!("Invalid fresh range: no end"))?
+            .parse::<i64>()?;
+        if parts.next().is_some() {
+            return Err(eyre!("Invalid fresh range: too many parts"));
+        }
+        Ok(FreshRange(start..=end))
+    }
+}
+
+impl Display for FreshRange {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}-{}", self.0.start(), self.0.end())
+    }
+}
+
+#[instrument(skip(input))]
+pub fn part1(input: &str) -> Result<usize> {
+    let mut processing_ranges = true;
+    let mut fresh_ranges = Vec::new();
+    let mut fresh_ingredients = 0;
+    for line in input.trim().lines() {
+        if line.is_empty() {
+            processing_ranges = false;
+            continue;
+        }
+        if processing_ranges {
+            let range = line.parse::<FreshRange>()?;
+            debug!(range = %range);
+            fresh_ranges.push(range);
+        } else {
+            let ingredient = line.parse::<i64>()?;
+            debug!(ingredient);
+            for range in &mut fresh_ranges {
+                if range.0.contains(&ingredient) {
+                    fresh_ingredients += 1;
+                    debug!(fresh_ingredients, "fresh!");
+                    break;
+                }
+            }
+        }
+    }
+    Ok(fresh_ingredients)
+}
+
+#[instrument(skip(input))]
+pub fn part2(input: &str) -> Result<usize> {
+    let mut fresh_ranges: Vec<Option<FreshRange>> = Vec::new();
+    for line in input.trim().lines() {
+        if line.is_empty() {
+            break;
+        }
+        let range = line.parse::<FreshRange>()?;
+        let mut overlap_range = range.clone();
+        debug!(range = %range);
+        for range_slot in fresh_ranges.iter_mut() {
+            if let Some(existing_range) = range_slot {
+                if overlap_range.0.end() < existing_range.0.start()
+                    || overlap_range.0.start() > existing_range.0.end()
+                {
+                    continue;
+                }
+                let start = *overlap_range.0.start().min(existing_range.0.start());
+                let end = *overlap_range.0.end().max(existing_range.0.end());
+                if start <= end {
+                    overlap_range = FreshRange(start..=end);
+                    debug!(overlap_range = %overlap_range, existing_range = %existing_range, "merging existing range");
+                    *range_slot = None; // this existing range is now completely merged with the current range
+                }
+            }
+        }
+        fresh_ranges.push(Some(overlap_range));
+    }
+    Ok(fresh_ranges
+        .iter()
+        .flatten()
+        .map(|r| (r.0.end() - r.0.start() + 1) as usize)
+        .sum())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_log::test;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(TEST_INPUT1).unwrap(), 3);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(TEST_INPUT1).unwrap(), 14);
+    }
+
+    #[test]
+    fn test_part2_triple_overlap() {
+        assert_eq!(part2("3-4\n2-5\n1-6").unwrap(), 6);
+    }
+}

src/day06/input/test1.txt

@@ -0,0 +1,4 @@
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +  

src/day06/mod.rs

@@ -0,0 +1,212 @@
+use std::str::FromStr;
+
+use color_eyre::{
+    Result,
+    eyre::{Context, Error, OptionExt, eyre},
+};
+use itertools::Itertools;
+use tracing::{debug, instrument};
+
+pub const INPUT: &str = include_str!("input/input.txt");
+
+#[derive(Debug, Clone, Copy)]
+enum Operation {
+    Add,
+    Multiply,
+}
+
+impl FromStr for Operation {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "+" => Ok(Operation::Add),
+            "*" => Ok(Operation::Multiply),
+            _ => Err(eyre!("invalid operation: {}", s)),
+        }
+    }
+}
+
+impl Operation {
+    fn from_byte(byte: u8) -> Result<Self> {
+        match byte {
+            b'+' => Ok(Operation::Add),
+            b'*' => Ok(Operation::Multiply),
+            _ => Err(eyre!("invalid operation byte: {}", byte)),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+struct Problem {
+    numbers: Vec<u64>,
+    operation: Operation,
+}
+
+#[derive(Debug, Clone)]
+struct CephalopodProblem {
+    columns: Vec<Vec<u8>>,
+    operation: Operation,
+    width: u8,
+}
+
+#[instrument(skip(input))]
+pub fn part1(input: &str) -> Result<u64> {
+    let mut lines = input.trim().lines();
+    let first_numbers: Vec<u64> = lines
+        .next()
+        .ok_or_eyre("no first line in input")?
+        .split_whitespace()
+        .map(|s| s.parse::<u64>().context("parsing number"))
+        .collect::<Result<Vec<u64>>>()?;
+    let mut problems = first_numbers
+        .into_iter()
+        .map(|n| Problem {
+            numbers: vec![n],
+            operation: Operation::Add,
+        })
+        .collect::<Vec<Problem>>();
+    for line in lines {
+        let first_byte = line.bytes().nth(0).ok_or_eyre("empty line in input")?;
+        if matches!(first_byte, b'*' | b'+') {
+            for (index, op_result) in line.split_whitespace().map(|s| s.parse()).enumerate() {
+                let op = op_result?;
+                problems[index].operation = op;
+            }
+        } else {
+            for (index, num_result) in line.split_whitespace().map(|s| s.parse()).enumerate() {
+                let num = num_result?;
+                problems[index].numbers.push(num);
+            }
+        }
+    }
+    Ok(problems
+        .into_iter()
+        .map(|problem| match problem.operation {
+            Operation::Add => {
+                let sum = problem.numbers.iter().sum::<u64>();
+                debug!("{} = {}", problem.numbers.iter().join(" + "), sum);
+                return sum;
+            }
+            Operation::Multiply => {
+                let product = problem.numbers.iter().product::<u64>();
+                debug!("{} = {}", problem.numbers.iter().join(" * "), product);
+                return product;
+            }
+        })
+        .sum())
+}
+
+#[instrument(skip(input))]
+pub fn part2(input: &str) -> Result<usize> {
+    let mut lines = input.lines();
+    let last_line = lines.next_back().ok_or_eyre("no last line in input")?;
+    let mut problems = Vec::new();
+    let mut spaces: u8 = 1;
+    for byte in last_line.bytes().rev() {
+        if byte.is_ascii_whitespace() {
+            spaces += 1;
+        } else {
+            problems.push(CephalopodProblem {
+                columns: (0..spaces).map(|_| Vec::new()).collect(),
+                operation: Operation::from_byte(byte)?,
+                width: spaces,
+            });
+            spaces = 0;
+        }
+    }
+    debug!(last_problem = ?problems[0]);
+    debug!(second_last_problem = ?problems[1]);
+    problems.reverse();
+    for line in lines {
+        let bytes = line.as_bytes();
+        let mut offset = 0;
+        for i in 0..problems.len() {
+            if offset + (problems[i].width as usize) > bytes.len() {
+                return Err(eyre!("line too short for problem columns"));
+            }
+            for (cell_col, &byte) in bytes[offset..offset + problems[i].width as usize]
+                .iter()
+                .enumerate()
+            {
+                if !byte.is_ascii_whitespace() {
+                    problems[i].columns[cell_col].push(byte - b'0');
+                }
+            }
+            offset += problems[i].width as usize + 1;
+        }
+    }
+    debug!(first_problem = ?problems[0]);
+    debug!(second_problem = ?problems[1]);
+    Ok(problems
+        .iter()
+        .map(|problem| match problem.operation {
+            Operation::Add => {
+                let sum: usize = problem
+                    .columns
+                    .iter()
+                    .map(|col| {
+                        col.iter()
+                            .fold(0usize, |acc, &digit| acc * 10 + (digit as usize))
+                    })
+                    .sum();
+                debug!(
+                    "{} = {}",
+                    problem
+                        .columns
+                        .iter()
+                        .map(|col| {
+                            col.iter()
+                                .fold(0usize, |acc, &digit| acc * 10 + (digit as usize))
+                                .to_string()
+                        })
+                        .join(" + "),
+                    sum
+                );
+                sum
+            }
+            Operation::Multiply => {
+                let product: usize = problem
+                    .columns
+                    .iter()
+                    .map(|col| {
+                        col.iter()
+                            .fold(0usize, |acc, &digit| acc * 10 + (digit as usize))
+                    })
+                    .product();
+                debug!(
+                    "{} = {}",
+                    problem
+                        .columns
+                        .iter()
+                        .map(|col| {
+                            col.iter()
+                                .fold(0usize, |acc, &digit| acc * 10 + (digit as usize))
+                                .to_string()
+                        })
+                        .join(" * "),
+                    product
+                );
+                product
+            }
+        })
+        .sum())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_log::test;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(TEST_INPUT1).unwrap(), 4277556);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(TEST_INPUT1).unwrap(), 3263827);
+    }
+}

src/days.rs

@@ -0,0 +1,16 @@
+// Single source of truth for all implemented days
+// Add new days here and they'll automatically be available in both the runner and benchmarks
+
+#[macro_export]
+macro_rules! all_days {
+    ($macro_name:path) => {
+        $macro_name! {
+            1 => day01,
+            2 => day02,
+            3 => day03,
+            4 => day04,
+            5 => day05,
+            6 => day06,
+        }
+    };
+}

src/lib.rs

@@ -0,0 +1,7 @@
+pub mod day01;
+pub mod day02;
+pub mod day03;
+pub mod day04;
+pub mod day05;
+pub mod day06;
+pub mod days;

src/main.rs

@@ -1,5 +1,8 @@
-pub mod day01;
+mod days;
+mod runner;
 
+use aoc::*;
+use clap::Parser;
 use color_eyre::Result;
 use tracing::info;
 use tracing_error::ErrorLayer;
@@ -7,6 +10,21 @@ use tracing_subscriber::EnvFilter;
 use tracing_subscriber::fmt::format::FmtSpan;
 use tracing_subscriber::prelude::*;
 
+#[derive(Parser, Debug)]
+#[command(name = "Advent of Code 2025")]
+#[command(about = "Solutions for Advent of Code 2025", long_about = None)]
+struct Args {
+    /// Day to run (1-25). If not specified, runs all days.
+    #[arg(short, long)]
+    day: Option<u8>,
+
+    /// Part to run (1 or 2). If not specified, runs all parts.
+    #[arg(short, long)]
+    part: Option<u8>,
+}
+
+all_days!(runner::days);
+
 fn main() -> Result<()> {
     color_eyre::install()?;
 
@@ -20,10 +38,12 @@ fn main() -> Result<()> {
         )
         .init();
 
+    let args = Args::parse();
+
     info!("Advent of Code 2025");
-    {
-        let _span = tracing::info_span!("aoc").entered();
-        day01::solve()?;
-    }
+    let _span = tracing::info_span!("aoc").entered();
+
+    run_days(args.day, args.part)?;
+
     Ok(())
 }

src/runner.rs

@@ -0,0 +1,57 @@
+use color_eyre::Result;
+use tracing::info;
+
+macro_rules! days {
+    ($($day_num:literal => $day_mod:ident),* $(,)?) => {
+        pub fn run_days(day: Option<u8>, part: Option<u8>) -> Result<()> {
+            match day {
+                $(
+                    Some($day_num) => $crate::runner::run_day($day_num, part, $day_mod::part1, $day_mod::part2, $day_mod::INPUT)?,
+                )*
+                Some(d) => color_eyre::eyre::bail!("Day {} is not yet implemented", d),
+                None => {
+                    $(
+                        $crate::runner::run_day($day_num, None, $day_mod::part1, $day_mod::part2, $day_mod::INPUT)?;
+                    )*
+                }
+            }
+            Ok(())
+        }
+    };
+}
+
+pub(crate) use days;
+
+pub fn run_day<T1, T2>(
+    day: u8,
+    part: Option<u8>,
+    part1_fn: fn(&str) -> Result<T1>,
+    part2_fn: fn(&str) -> Result<T2>,
+    input: &str,
+) -> Result<()>
+where
+    T1: std::fmt::Display,
+    T2: std::fmt::Display,
+{
+    info!("Day {}", day);
+    let day_name = format!("{:02}", day);
+    let _span = tracing::info_span!("day", day = %day_name).entered();
+
+    if part.is_none() || part == Some(1) {
+        let result = part1_fn(input)?;
+        info!("Part 1: {}", result);
+    }
+
+    if part.is_none() || part == Some(2) {
+        let result = part2_fn(input)?;
+        info!("Part 2: {}", result);
+    }
+
+    if let Some(p) = part {
+        if p != 1 && p != 2 {
+            color_eyre::eyre::bail!("Part {} is invalid. Must be 1 or 2.", p);
+        }
+    }
+
+    Ok(())
+}