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eight.rs
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eight.rs
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use std::collections::HashMap;
use libaoc::{Day, DayNumber};
pub fn decode(digits: &[&str], output: &[&str]) -> u32 {
assert_eq!(output.len(), 4);
assert_eq!(digits.len(), 10);
let mut byte_number: HashMap<u8, u8> = HashMap::new();
let mut number_byte: HashMap<u8, u8> = HashMap::new();
let mut bitmaps: Vec<u8> = digits
.iter()
.map(|&digit| {
let mut byte = 0u8;
for c in digit.chars() {
byte |= 1 << (c as u8 - b'a');
}
match digit.len() {
2 => {
byte_number.insert(byte, 1);
number_byte.insert(1, byte);
}
3 => {
byte_number.insert(byte, 7);
number_byte.insert(7, byte);
}
4 => {
byte_number.insert(byte, 4);
number_byte.insert(4, byte);
}
7 => {
byte_number.insert(byte, 8);
number_byte.insert(8, byte);
}
_ => (),
}
byte
})
.collect();
bitmaps.drain_filter(|map| number_byte.values().any(|&v| v == *map));
let six = bitmaps
.drain_filter(|map| {
(*map | (number_byte.get(&7).unwrap() ^ number_byte.get(&8).unwrap())) == *map
})
.last()
.unwrap();
number_byte.insert(6, six);
byte_number.insert(six, 6);
let five = bitmaps
.drain_filter(|map| (*map & number_byte.get(&6).unwrap()) == *map)
.last()
.unwrap();
number_byte.insert(5, five);
byte_number.insert(five, 5);
let nine = bitmaps
.drain_filter(|map| *map == number_byte.get(&5).unwrap() | number_byte.get(&4).unwrap())
.last()
.unwrap();
number_byte.insert(9, nine);
byte_number.insert(nine, 9);
let three = bitmaps
.drain_filter(|map| *map | number_byte.get(&9).unwrap() == *number_byte.get(&9).unwrap())
.last()
.unwrap();
byte_number.insert(three, 3);
let zero = bitmaps
.drain_filter(|map| *map & number_byte.get(&1).unwrap() == *number_byte.get(&1).unwrap())
.last()
.unwrap();
byte_number.insert(zero, 0);
let two = bitmaps[0];
byte_number.insert(two, 2);
let mut result = 0u32;
for (i, &out) in output.iter().enumerate() {
let mut out_byte = 0u8;
for c in out.chars() {
out_byte |= 1 << (c as u8 - b'a');
}
let mut pow10 = 1u32;
for _ in 0..(3 - i) {
pow10 *= 10;
}
result += pow10 * *byte_number.get(&out_byte).unwrap() as u32
}
result
}
pub fn eight() -> Day<2021> {
Day::new(
DayNumber::Eight,
|input| {
Box::new(
input
.lines()
.map(|line| {
line.split_once(" | ")
.unwrap()
.1
.split_whitespace()
.filter(|&d| [2, 3, 4, 7].contains(&d.len()))
.count()
})
.sum::<usize>(),
)
},
|input| {
let codes: Vec<(Vec<&str>, Vec<&str>)> = input
.lines()
.map(|line| line.split_once(" | ").unwrap())
.map(|(digits, out)| {
(
digits.split_whitespace().collect::<Vec<&str>>(),
out.split_whitespace().collect::<Vec<&str>>(),
)
})
.collect();
Box::new(
codes
.iter()
.map(|(digits, out)| decode(digits, out))
.sum::<u32>(),
)
},
)
}
#[cfg(test)]
mod tests {
fn parse_line(input: &str) -> (Vec<&str>, Vec<&str>) {
let (digits_str, out_str) = input.split_once(" | ").unwrap();
(
digits_str.split_whitespace().collect(),
out_str.split_whitespace().collect(),
)
}
#[test]
pub fn decode_seven_segments() {
use crate::{days, parse};
let inputs = parse!(
parse_line,
"be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe",
"edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc",
"fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg",
"fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb",
"aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea",
"fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb",
"dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe",
"bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef",
"egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb",
"gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce"
);
let results = vec![8394, 9781, 1197, 9361, 4873, 8418, 4548, 1625, 8717, 4315];
for ((a, b), &r) in inputs.iter().zip(results.iter()) {
assert_eq!(days::eight::decode(a, b), r);
}
}
}