jonas.tngl.sh
Advent of Code solutions in Rust
feat: day 15 of AoC 2020
Brute-forcing part 2 sometimes works...
+101
-2
+99
aoc_2020/src/day15.rs
+99
aoc_2020/src/day15.rs
···
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use std::{collections::HashMap, num::ParseIntError};
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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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starting_numbers: Vec<usize>,
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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, ParseIntError> {
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input
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.split(',')
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.map(str::parse)
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.try_collect()
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.map(|starting_numbers| Door { starting_numbers })
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}
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fn part1(&self) -> usize {
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Game::from(self.starting_numbers.iter().copied())
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.nth(2019)
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.unwrap()
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}
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fn part2(&self) -> usize {
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Game::from(self.starting_numbers.iter().copied())
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.nth(29_999_999)
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.unwrap()
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}
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}
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struct Game<I: Iterator<Item = usize>> {
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starting_numbers: I,
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next: Option<usize>,
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n: usize,
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last_seen: HashMap<usize, usize>,
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}
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impl<I: Iterator<Item = usize>> Game<I> {
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fn from(starting_numbers: impl IntoIterator<Item = usize, IntoIter = I>) -> Self {
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Self {
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starting_numbers: starting_numbers.into_iter(),
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next: None,
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n: 0,
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last_seen: HashMap::new(),
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}
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}
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}
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impl<I: Iterator<Item = usize>> Iterator for Game<I> {
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type Item = usize;
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fn next(&mut self) -> Option<Self::Item> {
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let current = self.starting_numbers.next().or_else(|| self.next.take())?;
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self.n += 1;
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if let Some(before) = self.last_seen.insert(current, self.n) {
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self.next = Some(self.n - before);
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} else {
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self.next = Some(0);
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}
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Some(current)
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}
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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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#[test]
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fn example_game_number_sequence() {
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itertools::assert_equal(
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Game::from([0, 3, 6]).take(10),
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[0, 3, 6, 0, 3, 3, 1, 0, 4, 0],
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);
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}
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#[test]
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fn correct_2020th_number() {
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assert_eq!(Game::from([0, 3, 6]).nth(2019), Some(436));
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assert_eq!(Game::from([1, 3, 2]).nth(2019), Some(1));
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assert_eq!(Game::from([2, 1, 3]).nth(2019), Some(10));
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assert_eq!(Game::from([1, 2, 3]).nth(2019), Some(27));
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assert_eq!(Game::from([2, 3, 1]).nth(2019), Some(78));
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assert_eq!(Game::from([3, 2, 1]).nth(2019), Some(438));
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assert_eq!(Game::from([3, 1, 2]).nth(2019), Some(1836));
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}
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#[test]
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#[ignore = "slow"]
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fn correct_30_000_000th_number() {
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assert_eq!(Game::from([0, 3, 6]).nth(29_999_999), Some(175594));
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assert_eq!(Game::from([1, 3, 2]).nth(29_999_999), Some(2578));
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assert_eq!(Game::from([2, 1, 3]).nth(29_999_999), Some(3544142));
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assert_eq!(Game::from([1, 2, 3]).nth(29_999_999), Some(261214));
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assert_eq!(Game::from([2, 3, 1]).nth(29_999_999), Some(6895259));
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assert_eq!(Game::from([3, 2, 1]).nth(29_999_999), Some(18));
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assert_eq!(Game::from([3, 1, 2]).nth(29_999_999), Some(362));
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}
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}
+2
-2
aoc_2020/src/main.rs
+2
-2
aoc_2020/src/main.rs
···
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mod day12;
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mod day13;
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mod day14;
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-
// mod day15;
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mod day15;
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// mod day16;
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// mod day17;
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// mod day18;
···
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door!(2020-12-12 ~> day12),
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door!(2020-12-13 ~> day13),
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door!(2020-12-14 ~> day14),
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-
// door!(2020-12-15 ~> day15),
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door!(2020-12-15 ~> day15),
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// door!(2020-12-16 ~> day16),
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// door!(2020-12-17 ~> day17),
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// door!(2020-12-18 ~> day18),