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use std::collections::HashSet;
static DAY: u8 = 4;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", total_points(&input));
println!("{DAY}b: {}", total_cards(&input));
}
struct Card {
winning_numbers: HashSet<u32>,
numbers_you_have: HashSet<u32>,
}
impl Card {
fn new(input: &str) -> Card {
let (_id, numbers) = input.split_once(": ").unwrap();
let (win, have) = numbers.split_once(" | ").unwrap();
let winning_numbers = win.split(' ')
.filter(|x| !x.is_empty())
.map(|x| x.parse().unwrap())
.collect::<HashSet<_>>();
let numbers_you_have = have.split(' ')
.filter(|x| !x.is_empty())
.map(|x| x.parse().unwrap())
.collect::<HashSet<_>>();
Card { winning_numbers, numbers_you_have }
}
fn matching_numbers(&self) -> HashSet<u32> {
self.winning_numbers.intersection(&self.numbers_you_have).copied().collect()
}
fn points(&self) -> u32 {
(1 << self.matching_numbers().len()) / 2
}
}
fn total_points(input: &[String]) -> u32 {
input.iter()
.map(|x| Card::new(x))
.map(|c| c.points())
.sum()
}
fn total_cards(input: &[String]) -> u32 {
let cards = input.iter()
.map(|x| Card::new(x))
.collect::<Vec<_>>();
let mut amounts = vec![1; cards.len()];
for (i, card) in cards.iter().enumerate() {
let matches = card.matching_numbers().len();
let copies = amounts[i];
for amount in amounts.iter_mut().take(i + 1 + matches).skip(i + 1) {
*amount += copies;
}
}
amounts.iter().sum()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"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",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(total_points(&input), 13);
assert_eq!(total_cards(&input), 30);
}
}
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