2025 day 1

Author: ictrobot

Cargo.lock

@@ -16,15 +16,16 @@ year2017 = { path = "../year2017", optional = true }
 year2018 = { path = "../year2018", optional = true }
 year2019 = { path = "../year2019", optional = true }
 year2024 = { path = "../year2024", optional = true }
+year2025 = { path = "../year2025", optional = true }
 
 [features]
 default = ["all-years", "all-simd", "unsafe", "test-runner"]
 const_lut = ["year2024?/const_lut"]
 all-simd = ["utils/all-simd"]
 test-runner = []
 # xtask update features
-all-years = ["year2015", "year2016", "year2017", "year2018", "year2019", "year2024"]
-unsafe = ["year2015?/unsafe", "year2016?/unsafe", "year2017?/unsafe", "year2018?/unsafe", "year2019?/unsafe", "year2024?/unsafe", "utils/unsafe"]
+all-years = ["year2015", "year2016", "year2017", "year2018", "year2019", "year2024", "year2025"]
+unsafe = ["year2015?/unsafe", "year2016?/unsafe", "year2017?/unsafe", "year2018?/unsafe", "year2019?/unsafe", "year2024?/unsafe", "year2025?/unsafe", "utils/unsafe"]
 
 [lints]
 workspace = true

crates/aoc/Cargo.toml

@@ -35,6 +35,10 @@ pub mod year2019 {
 pub mod year2024 {
     pub use ::utils::puzzles_noop as puzzles;
 }
+#[cfg(not(feature = "year2025"))]
+pub mod year2025 {
+    pub use ::utils::puzzles_noop as puzzles;
+}
 #[cfg(feature = "year2015")]
 pub use ::year2015;
 #[cfg(feature = "year2016")]
@@ -47,6 +51,8 @@ pub use ::year2018;
 pub use ::year2019;
 #[cfg(feature = "year2024")]
 pub use ::year2024;
+#[cfg(feature = "year2025")]
+pub use ::year2025;
 
 /// Macro which invokes a callback macro with a list of all implemented puzzle solutions.
 ///
@@ -119,6 +125,7 @@ macro_rules! all_puzzles {
                 $crate::year2018::puzzles,
                 $crate::year2019::puzzles,
                 $crate::year2024::puzzles,
+                $crate::year2025::puzzles,
 
                 $callback
             ]

crates/aoc/src/years.rs

@@ -0,0 +1,14 @@
+[package]
+name = "year2025"
+authors = { workspace = true }
+edition = { workspace = true }
+license = { workspace = true }
+publish = { workspace = true }
+repository = { workspace = true }
+rust-version = { workspace = true }
+
+[dependencies]
+utils = { path = "../utils", default-features = false }
+
+[features]
+unsafe = ["utils/unsafe"]

crates/year2025/Cargo.toml

@@ -0,0 +1 @@
+Solutions for [Advent of Code 2025](https://adventofcode.com/2025)

crates/year2025/README.md

@@ -0,0 +1,54 @@
+use utils::prelude::*;
+
+/// Counting how many times a dial passes zero.
+#[derive(Clone, Debug)]
+pub struct Day01 {
+    turns: Vec<(Direction, i32)>,
+}
+
+parser::parsable_enum! {
+    #[derive(Clone, Copy, Debug)]
+    enum Direction {
+        "L" => Left = -1,
+        "R" => Right = 1,
+    }
+}
+
+impl Day01 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        Ok(Self {
+            turns: Direction::PARSER
+                .then(parser::number_range(1i32..=999))
+                .parse_lines(input)?,
+        })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> u32 {
+        let mut zero_count = 0;
+        let mut pos = 50;
+        for &(dir, steps) in &self.turns {
+            pos = (pos + (steps * dir as i32)).rem_euclid(100);
+            zero_count += u32::from(pos == 0);
+        }
+        zero_count
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> u32 {
+        let mut zero_count = 0;
+        let mut pos = 50;
+        for &(dir, steps) in &self.turns {
+            zero_count += match dir {
+                Direction::Left => ((100 - pos + steps) / 100) as u32 - u32::from(pos == 0),
+                Direction::Right => ((pos + steps) / 100) as u32,
+            };
+            pos = (pos + (steps * dir as i32)).rem_euclid(100);
+        }
+        zero_count
+    }
+}
+
+examples!(Day01 -> (u32, u32) [
+    {input: "L68\nL30\nR48\nL5\nR60\nL55\nL1\nL99\nR14\nL82", part1: 3, part2: 6},
+]);

crates/year2025/src/day01.rs

@@ -0,0 +1,6 @@
+#![doc = include_str!("../README.md")]
+#![cfg_attr(not(feature = "unsafe"), forbid(unsafe_code))]
+
+utils::year!(2025 => year2025, ${
+    1 => day01::Day01,
+});