advent-of-code/2021/day8/rust/src/v2.rs
2022-12-01 19:24:06 +01:00

47 lines
1 KiB
Rust

use crate::LineResult;
use arrayvec::ArrayVec;
const FREQ_TABLE: [usize; 50] = {
let mut tab = [0; 50];
tab[17] = 1;
tab[25] = 7;
tab[30] = 4;
tab[34] = 2;
tab[37] = 5;
tab[39] = 3;
tab[41] = 6;
tab[42] = 0;
tab[45] = 9;
tab[49] = 8;
tab
};
#[must_use]
#[inline]
pub fn unscramble(line: &str) -> LineResult {
let mut parts = line.split('|');
let input = parts.next().unwrap();
let mut counts = [0; 7];
for c in input.bytes() {
if (b'a'..=b'g').contains(&c) {
counts[c as usize - b'a' as usize] += 1;
}
}
let digits = parts
.next()
.unwrap()
.trim_start()
.split(' ')
.map(|s| s.bytes().map(|c| counts[c as usize - b'a' as usize]).sum())
.map(|n: usize| FREQ_TABLE[n])
.collect::<ArrayVec<_, 4>>()
.into_inner()
.unwrap();
LineResult {
unique_digits: digits.iter().filter(|d| [1, 4, 7, 8].contains(d)).count(),
number: digits.iter().fold(0, |acc, d| acc * 10 + d),
}
}