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use {
anyhow::{
anyhow,
Context,
Result,
},
std::{
collections::HashSet,
env::args,
fs::File,
hash::{
Hash,
Hasher,
},
io::{
BufRead,
BufReader,
},
path::Path,
str::FromStr,
},
thiserror::Error,
};
#[derive(Error, Debug)]
enum SegmentError {
#[error("Invalid segment character")]
Invalid(char),
}
type SegmentResult<T> = std::result::Result<T, SegmentError>;
#[derive(Clone,Debug,Eq,Hash,Ord,PartialEq,PartialOrd)]
enum Segment { A, B, C, D, E, F, G, }
#[derive(Clone,Debug,Eq)]
struct Digit {
inner: HashSet<Segment>,
}
// https://stackoverflow.com/q/36562419/hashset-as-key-for-other-hashset
impl Hash for Digit {
fn hash<H>(&self, state: &mut H) where H: Hasher {
let mut a: Vec<&Segment> = self.inner.iter().collect();
a.sort();
for s in a.iter() {
s.hash(state);
}
}
}
impl PartialEq for Digit {
fn eq(&self, other: &Digit) -> bool {
self.inner == other.inner
}
}
impl FromStr for Digit {
type Err = SegmentError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let inner = s.chars().map(|c| match c {
'a' => Ok(Segment::A),
'b' => Ok(Segment::B),
'c' => Ok(Segment::C),
'd' => Ok(Segment::D),
'e' => Ok(Segment::E),
'f' => Ok(Segment::F),
'g' => Ok(Segment::G),
_ => Err(SegmentError::Invalid(c)),
}).collect::<SegmentResult<HashSet<Segment>>>()?;
Ok(Self {
inner,
})
}
}
#[derive(Debug)]
struct Signals {
input: Vec<Digit>,
output: Vec<Digit>,
}
fn read_signals<T: AsRef<Path>>(filename: T) -> Result<Vec<Signals>> {
let reader = BufReader::new(File::open(filename)?);
reader.lines().map(
|row| {
let r = row?;
let (left, right) = r.split_once('|')
.ok_or_else(|| anyhow!("Missing separator: {}", r))?;
let input = left.split_whitespace().map(|n| n.parse()
.map_err(|err| anyhow!("{}", err))).collect::<Result<Vec<Digit>>>()?;
let output = right.split_whitespace().map(|n| n.parse()
.map_err(|err| anyhow!("{}", err))).collect::<Result<Vec<Digit>>>()?;
Ok(Signals {input, output})
}
).collect()
}
fn part1<'a, I: IntoIterator<Item = &'a Signals>>(signals: I) -> Result<usize> {
// aaaa .... aaaa aaaa ....
// b c . c . c . c b c
// b c . c . c . c b c
// .... .... dddd dddd dddd
// e f . f e . . f . f
// e f . f e . . f . f
// gggg .... gggg gggg ....
//
// 5: 6: 7: 8: 9:
// aaaa aaaa aaaa aaaa aaaa
// b . b . . c b c b c
// b . b . . c b c b c
// dddd dddd .... dddd dddd
// . f e f . f e f . f
// . f e f . f e f . f
// gggg gggg .... gggg gggg
// 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
let segment_count = [6, 2, 5, 5, 4, 5, 6, 3, 7, 6];
let count = signals.into_iter().map(|s| {
let c: usize = s.output.iter().map(|d| {
match d.inner.len() {
v if v == segment_count[1] ||
v == segment_count[4] ||
v == segment_count[7] ||
v == segment_count[8] => 1,
_ => 0,
}
}).sum();
c
}).sum();
Ok(count)
}
fn find_digits(input: &[Digit]) -> Result<Vec<Option<Digit>>> {
let segment_count = [6, 2, 5, 5, 4, 5, 6, 3, 7, 6];
let mut digits: Vec<Option<Digit>> = vec![None; 10];
let mut unknown = HashSet::new();
for digit in input.iter() {
unknown.insert(digit.clone());
}
for unique_segments in [1, 4, 7, 8].into_iter() {
// Digit 1 is found by unique number of segments, as in part 1.
// The same is true for Digit 4, Digit 7 and Digit 8.
unknown.clone().into_iter().map(|d| if d.inner.len() == segment_count[unique_segments] {
unknown.remove(&d);
digits[unique_segments] = Some(d);
}).last();
}
// Digit 3 is the only five segmented superset of Digit 1 (and Digit 7).
digits[3] = unknown.clone().into_iter().filter(|d| {
if d.inner.len() == 5 {
if let Some(one) = &digits[1] {
if d.inner.is_superset(&one.inner) {
unknown.remove(d);
return true;
}
}
}
false
}).last();
// Digit 0 is Digit 8 - (Digit 3 & (Digit 4 - Digit 1)).
digits[0] = unknown.clone().into_iter().filter(|d| {
if let (Some(one), Some(three), Some(four), Some(eight)) =
(&digits[1], &digits[3], &digits[4], &digits[8])
{
if d.inner == &eight.inner - &(&three.inner & &(&four.inner - &one.inner)) {
unknown.remove(d);
return true
}
}
false
}).last();
digits[9] = unknown.clone().into_iter().filter(|d| {
if d.inner.len() == 6 {
if let Some(three) = &digits[3] {
if d.inner.is_superset(&three.inner) {
unknown.remove(d);
return true
}
}
}
false
}).last();
// Digit 6 is the only remaining six segmented unknown.
digits[6] = unknown.clone().into_iter().filter(|d| if d.inner.len() == 6 {
unknown.remove(d);
true
} else {
false
}).last();
// Digit 2 is the one with zero overlap with the difference of Digit 4 - Digit 3.
digits[2] = unknown.clone().into_iter().filter(|d| {
if let (Some(three), Some(four)) = (&digits[3], &digits[4]) {
if (&d.inner & &(&four.inner - &three.inner)).is_empty() {
unknown.remove(d);
return true
}
}
false
}).last();
// Digit 5 is the remaining one.
digits[5] = unknown.into_iter().next();
Ok(digits)
}
fn decode_output(output: &[Digit], digits: &[Option<Digit>]) -> Result<usize> {
output.iter().fold(Ok(0), |acc, d| {
let mut acc_val = acc.expect("Bug in decode_output()");
acc_val *= 10;
(0..=9).filter_map(|n|
match digits.get(n)? {
Some(i) if i.inner == d.inner => Some(acc_val + n),
_ => None,
}
).next().ok_or(anyhow!("No digit matched"))
})
}
fn part2<'a, I: IntoIterator<Item = &'a Signals>>(signals: I) -> Result<usize> {
let res: usize = signals.into_iter().map(|signal| {
let digits = find_digits(&signal.input)?;
decode_output(&signal.output, &digits)
}).collect::<Result<Vec<_>>>()?.into_iter().sum();
Ok(res)
}
fn main() -> Result<()> {
let ( do_part_1, do_part_2 ) = aoc::do_parts();
let filename = args().nth(1).ok_or(anyhow!("Missing signals filename"))?;
let signals = read_signals(filename).context("Could not read signals")?;
if do_part_1 {
let solution = part1(&signals).context("No solution for part 1")?;
println!("Part1, solution found to be: {}", solution);
}
if do_part_2 {
let solution = part2(&signals).context("No solution for part 2")?;
println!("Part2, solution found to be: {}", solution);
}
Ok(())
}
|
