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use crate::{Problem, Solution};
pub struct Day04;
impl Problem for Day04 {
const DAY: u8 = 4;
const INPUT: &'static str = include_str!("../input/day_04.txt");
}
impl Solution for Day04 {
type Answer1 = usize;
type Answer2 = usize;
fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
let scores = input
.trim()
.split('\n')
.map(parse_score)
.collect::<Result<Vec<_>, _>>()?;
Ok(scores
.into_iter()
.filter(|n| n > &0)
.map(|n| 2usize.pow(n as u32 - 1))
.sum())
}
fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
let scores = input
.trim()
.split('\n')
.map(parse_score)
.collect::<Result<Vec<_>, _>>()?;
let cards = &mut vec![0usize; scores.len()];
for card in 0..scores.len() {
add_copy(cards, &scores, card)
}
Ok(cards.iter().sum())
}
}
fn add_copy(cards: &mut Vec<usize>, scores: &[usize], card: usize) {
cards[card] += 1;
for card in card + 1..cards.len().min(card + scores[card] + 1) {
add_copy(cards, scores, card);
}
}
fn parse_score(s: &str) -> anyhow::Result<usize> {
let (winning, numbers) = s
.trim()
.split_once(':')
.ok_or(anyhow::format_err!("Invalid card format: {s}"))?
.1
.trim()
.split_once('|')
.ok_or(anyhow::format_err!("Invalid card format: {s}"))?;
let winning_set = winning
.split_whitespace()
.map(std::str::FromStr::from_str)
.collect::<Result<Vec<usize>, _>>()?;
Ok(numbers
.split_whitespace()
.map(std::str::FromStr::from_str)
.collect::<Result<Vec<usize>, _>>()?
.into_iter()
.filter(|n| winning_set.contains(n))
.count())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_part_1() -> anyhow::Result<()> {
const INPUT: &str = indoc::indoc! {"
Card 1: 41 48 83 86 17 | 83 86 6 31 17 9 48 53
Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
Card 3: 1 21 53 59 44 | 69 82 63 72 16 21 14 1
Card 4: 41 92 73 84 69 | 59 84 76 51 58 5 54 83
Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
"};
Ok(assert_eq!(13, Day04::part_1(INPUT)?))
}
#[test]
fn test_part_2() -> anyhow::Result<()> {
const INPUT: &str = indoc::indoc! {"
Card 1: 41 48 83 86 17 | 83 86 6 31 17 9 48 53
Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
Card 3: 1 21 53 59 44 | 69 82 63 72 16 21 14 1
Card 4: 41 92 73 84 69 | 59 84 76 51 58 5 54 83
Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
"};
Ok(assert_eq!(30, Day04::part_2(INPUT)?))
}
}
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