jonas.tngl.sh
Advent of Code solutions in Rust
feat: complete AoC 2025 ⭐️
+125
-2
+1
Cargo.lock
+1
Cargo.lock
+1
aoc_2025/Cargo.toml
+1
aoc_2025/Cargo.toml
+121
aoc_2025/src/day12.rs
+121
aoc_2025/src/day12.rs
···
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use std::{collections::HashSet, num::ParseIntError};
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use anyhow::{Context, anyhow, bail};
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use aoc_companion::prelude::*;
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use itertools::Itertools as _;
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pub(crate) struct Door {
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problems: Vec<Problem>,
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}
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impl<'input> Solution<'input> for Door {
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fn parse(input: &'input str) -> Result<Self> {
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let Some((shapes, problems)) = input.rsplit_once("\n\n") else {
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bail!("could not find empty line delimiting shapes and problems");
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};
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let shapes_hash = fxhash::hash(shapes);
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if shapes_hash != 0x2050bd894f01430f {
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bail!("solution only works for my input; got different hash: {shapes_hash:x}");
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}
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problems
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.lines()
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.map(str::parse)
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.try_collect()
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.map(|problems| Door { problems })
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}
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fn part1(&self) -> Result<usize> {
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let (conclusive, inconclusive): (Vec<bool>, HashSet<&Problem>) = self
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.problems
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.iter()
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.map(|problem| {
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rule_out_due_to_insufficient_area(problem)
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.or_else(|| verify_with_trivial_packing(problem))
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.ok_or(problem)
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})
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.partition_result();
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if !inconclusive.is_empty() {
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bail!(
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"{}/{} problems were inconclusive, e.g.: {}",
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inconclusive.len(),
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self.problems.len(),
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inconclusive.iter().next().unwrap()
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);
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}
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Ok(conclusive.into_iter().filter(|&b| b).count())
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}
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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struct Problem {
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dimensions: [usize; 2],
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presents: [usize; 6],
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}
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impl std::fmt::Display for Problem {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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write!(
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f,
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"{}: {}",
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self.dimensions.iter().join("x"),
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self.presents.iter().join(" ")
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)
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}
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}
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impl std::str::FromStr for Problem {
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type Err = anyhow::Error;
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fn from_str(s: &str) -> Result<Self> {
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let Some((dimensions, shapes)) = s.split_once(':') else {
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bail!("could not find colon delimiting problem dimensions and required shapes");
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};
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let dimensions = dimensions
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.split_once('x')
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.ok_or_else(|| anyhow!("missing 'x' in dimensions spec {dimensions:?}"))
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.and_then(|(x, y)| {
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Ok::<_, ParseIntError>([x.parse()?, y.parse()?])
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.with_context(|| anyhow!("failed to parse region dimenions {dimensions:?}"))
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})?;
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// TODO: add try_from_iter_exact
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let presents = aoc_utils::array::try_from_iter(shapes.split_whitespace().map(|s| {
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s.parse()
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.with_context(|| anyhow!("failed to parse present count {s:?}"))
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}))?
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.map_err(|e| anyhow!("wrong number of presents: expected 6, got {}", e.len()))?;
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Ok(Self {
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dimensions,
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presents,
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})
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}
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}
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impl Problem {
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fn area(&self) -> usize {
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self.dimensions[0] * self.dimensions[1]
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}
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}
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fn rule_out_due_to_insufficient_area(problem: &Problem) -> Option<bool> {
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const AREA: [usize; 6] = [5, 7, 7, 7, 6, 7];
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let required_area: usize = problem
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.presents
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.iter()
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.zip(AREA)
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.map(|(count, area)| count * area)
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.sum();
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(required_area > problem.area()).then_some(false)
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}
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fn verify_with_trivial_packing(problem: &Problem) -> Option<bool> {
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let available_cells = (problem.dimensions[0] / 3) * (problem.dimensions[1] / 3);
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let total_presents: usize = problem.presents.iter().sum();
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(total_presents <= available_cells).then_some(true)
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}
+2
-2
aoc_2025/src/main.rs
+2
-2
aoc_2025/src/main.rs
···
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mod day09;
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mod day10;
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mod day11;
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-
// mod day12;
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mod day12;
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use aoc_companion::prelude::*;
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···
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door!(2025-12-09 ~> day09),
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door!(2025-12-10 ~> day10),
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door!(2025-12-11 ~> day11),
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-
// door!(2025-12-12 ~> day12),
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door!(2025-12-12 ~> day12),
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])
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.await
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}