jonas.tngl.sh
Advent of Code solutions in Rust
feat: day 3 of AoC 2025
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-2
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aoc_2025/src/day03.rs
+86
aoc_2025/src/day03.rs
···
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use anyhow::Context as _;
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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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banks: Vec<Vec<u32>>,
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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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Ok(Door {
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banks: input
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.lines()
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.map(|line| {
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line.chars()
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.map(|c| {
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c.to_digit(10)
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.with_context(|| anyhow::anyhow!("{c:?} is not a digit"))
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})
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.try_collect()
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})
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.try_collect()?,
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})
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}
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fn part1(&self) -> u64 {
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self.banks.iter().map(|b| max_joltage(b, 2)).sum()
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}
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fn part2(&self) -> u64 {
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self.banks.iter().map(|b| max_joltage(b, 12)).sum()
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}
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}
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fn max_joltage(bank: &[u32], n_battery: usize) -> u64 {
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let (res, _) = (0..n_battery).rev().fold((0, bank), |(acc, available), n| {
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let rev_pos = available.iter().rev().skip(n).position_max().unwrap() + n;
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let max_idx = available.len() - rev_pos - 1;
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let (max, rest) = available[max_idx..].split_first().unwrap();
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(acc * 10 + *max as u64, rest)
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});
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res
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const EXAMPLE_INPUT: &str = "\
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987654321111111
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811111111111119
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234234234234278
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818181911112111";
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const EXAMPLE_BANKS: [[u32; 15]; 4] = [
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[9, 8, 7, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 1, 1],
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[8, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9],
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[2, 3, 4, 2, 3, 4, 2, 3, 4, 2, 3, 4, 2, 7, 8],
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[8, 1, 8, 1, 8, 1, 9, 1, 1, 1, 1, 2, 1, 1, 1],
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];
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#[test]
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fn parse_example_input() {
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let Door { banks } = Door::parse(EXAMPLE_INPUT).unwrap();
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itertools::assert_equal(banks, EXAMPLE_BANKS);
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}
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#[test]
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fn max_joltage_for_multiple_repeats() {
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assert_eq!(max_joltage(&[9, 9, 1], 2), 99);
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}
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#[test]
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fn example_max_joltages_of_2_batteries() {
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itertools::assert_equal(EXAMPLE_BANKS.map(|b| max_joltage(&b, 2)), [98, 89, 78, 92]);
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}
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#[test]
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fn example_max_joltages_of_12_batteries() {
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itertools::assert_equal(
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EXAMPLE_BANKS.map(|b| max_joltage(&b, 12)),
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[987654321111, 811111111119, 434234234278, 888911112111],
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);
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}
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}
+2
-2
aoc_2025/src/main.rs
+2
-2
aoc_2025/src/main.rs
···
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mod day01;
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mod day02;
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// mod day03;
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mod day03;
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// mod day04;
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// mod day05;
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// mod day06;
···
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aoc_main(&[
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door!(2025-12-01 ~> day01),
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door!(2025-12-02 ~> day02),
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-
// door!(2025-12-03 ~> day03),
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door!(2025-12-03 ~> day03),
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// door!(2025-12-04 ~> day04),
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// door!(2025-12-05 ~> day05),
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// door!(2025-12-06 ~> day06),