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Day 8 Refactoring III 

Completely remove SevenSegmentDisplay type
This commit is contained in:
kageru 2021-12-08 16:54:07 +01:00
parent 83419cbdf3
commit a1f6eb888c
1 changed files with 14 additions and 33 deletions
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47
2021/src/bin/day08.rs
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@ -5,16 +5,15 @@
extern crate test;
use aoc2021::common::*;
use itertools::{iproduct, Itertools};
use std::{array, lazy::Lazy, ops};
use std::{array, lazy::Lazy};
const DAY: usize = 08;
const DAY: usize = 8;
type Parsed<'a> = Vec<([&'a str; 10], [&'a str; 4])>;
const VALID_DISPLAYS: Lazy<[SSD; 10]> =
Lazy::new(|| ["abcefg", "cf", "acdeg", "acdfg", "bcdf", "abdfg", "abdefg", "acf", "abcdefg", "abcdfg"].map(SSD::from));
Lazy::new(|| ["abcefg", "cf", "acdeg", "acdfg", "bcdf", "abdfg", "abdefg", "acf", "abcdefg", "abcdfg"].map(parse));
#[derive(Debug, PartialEq)]
struct SSD([bool; 7]);
type SSD = [bool; 7];
struct Mapping([char; 7]);
@ -24,27 +23,12 @@ impl Mapping {
}
}
impl From<&str> for SSD {
fn from(s: &str) -> Self {
SSD([s.contains('a'), s.contains('b'), s.contains('c'), s.contains('d'), s.contains('e'), s.contains('f'), s.contains('g')])
}
fn parse(s: &str) -> SSD {
[s.contains('a'), s.contains('b'), s.contains('c'), s.contains('d'), s.contains('e'), s.contains('f'), s.contains('g')]
}
impl ops::Sub<&SSD> for &SSD {
type Output = SSD;
fn sub(self, rhs: &SSD) -> Self::Output {
SSD(self.0.zip(rhs.0).map(|(l, r)| l && !r))
}
}
impl SSD {
fn active_digits(&self) -> u8 {
self.0.iter().map(|&b| b as u8).sum()
}
fn to_array(&self) -> [bool; 7] {
self.0
}
fn difference(lhs: &SSD, rhs: &SSD) -> SSD {
lhs.zip(*rhs).map(|(l, r)| l && !r)
}
fn parse_input(raw: &str) -> Parsed {
@ -66,18 +50,15 @@ fn part2<'a>(parsed: &Parsed<'a>) -> usize {
parsed
.iter()
.map(|(raw_input, raw_output)| {
let input = raw_input.map(SSD::from);
let one = input.iter().find(|d| d.active_digits() == 2).unwrap();
let four = input.iter().find(|d| d.active_digits() == 4).unwrap();
let seven = input.iter().find(|d| d.active_digits() == 3).unwrap();
let [one, four, seven] = [2, 4, 3].map(|n| raw_input.iter().find(|s| s.len() == n).unwrap()).map(|&s| parse(s));
// We know the position of a for sure because it’s the only difference between 7 and 1
let a = (seven - one).to_array().iter().position(|&b| b).unwrap();
let a = difference(&seven, &one).iter().position(|&b| b).unwrap();
// And c and f are these two (both used in 1).
// Countrary to the name, these two values are both c_or_f,
// so we know c and f are these two, but we don’t know which is which.
let (c, f) = one.to_array().iter().positions(|&b| b).next_tuple().unwrap();
let (c, f) = one.iter().positions(|&b| b).next_tuple().unwrap();
// 4 uses b, c, d, f, but we already know c and f from 1, so this leaves b and d.
let (b, d) = (four - one).to_array().iter().positions(|&b| b).next_tuple().unwrap();
let (b, d) = difference(&four, &one).iter().positions(|&b| b).next_tuple().unwrap();
// Now e and g have to be in the remaining two positions.
let (e, g) = (0..7).filter(|n| ![a, b, c, d, f].contains(n)).next_tuple().unwrap();
debug_assert_eq!([a, b, c, d, e, f, g].into_iter().sorted().collect_vec(), (0..7).collect_vec());
@ -97,7 +78,7 @@ fn part2<'a>(parsed: &Parsed<'a>) -> usize {
.find(|m| {
raw_input.iter().all(|i| {
let translated: String = i.chars().map(|n| m.translate(n)).collect();
let ssd = SSD::from(translated.as_ref());
let ssd = parse(&translated);
VALID_DISPLAYS.iter().any(|d| d == &ssd)
})
})
@ -105,7 +86,7 @@ fn part2<'a>(parsed: &Parsed<'a>) -> usize {
raw_output
.iter()
.map(|i| i.chars().map(|n| mapping.translate(n)).collect::<String>())
.map(|t| SSD::from(t.as_ref()))
.map(|t| parse(&t))
.map(|ssd| VALID_DISPLAYS.iter().position(|d| &ssd == d).unwrap())
.fold(0, |acc, n| (acc + n) * 10)
/ 10