1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
use nom::{
bytes::complete::tag,
character::complete::{line_ending, space1, u32 as nom_u32},
combinator::map,
multi::separated_list1,
sequence::tuple,
IResult,
};
use std::{collections::BTreeSet, fs};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_4.txt")?;
let parsed = Scratchcards::parser(&input).unwrap().1;
dbg!(&parsed.points());
dbg!(&parsed.scratchcard_explosion_sum());
Ok(())
}
#[derive(Debug)]
struct Scratchcards(Vec<Scratchcard>);
#[derive(Debug)]
struct Scratchcard {
winning: BTreeSet<u32>,
owned: BTreeSet<u32>,
}
impl Scratchcards {
fn parser(input: &str) -> IResult<&str, Self> {
map(
separated_list1(line_ending, Scratchcard::parser),
Scratchcards,
)(input)
}
fn points(&self) -> usize {
self.0.iter().map(|card| card.points()).sum()
}
fn scratchcard_explosion_sum(&self) -> u64 {
let mut scratchcard_pile = vec![1_u64.into(); self.0.len()];
for i in 0..scratchcard_pile.len() {
let points = self.0[i].winning_numbers();
let new_scratchcards: u64 = scratchcard_pile[i];
for offset in 0..points {
if let Some(pile) = scratchcard_pile.get_mut(i + 1 + offset) {
*pile += new_scratchcards;
}
}
}
scratchcard_pile.into_iter().sum()
}
}
impl Scratchcard {
fn parser(input: &str) -> IResult<&str, Self> {
map(
tuple((
tag("Card"),
space1,
nom_u32,
tag(":"),
space1,
separated_list1(space1, nom_u32),
space1,
tag("|"),
space1,
separated_list1(space1, nom_u32),
)),
|(_, _, _, _, _, winning, _, _, _, owned)| Scratchcard {
winning: winning.into_iter().collect(),
owned: owned.into_iter().collect(),
},
)(input)
}
fn winning_numbers(&self) -> usize {
self.winning.intersection(&self.owned).count()
}
fn points(&self) -> usize {
let winning_numbers = self.winning_numbers();
if winning_numbers > 0 {
2_usize.pow(winning_numbers as u32 - 1)
} else {
0
}
}
}
|
