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author | June McEnroe <june@causal.agency> | 2016-12-04 14:17:42 -0500 |
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committer | June McEnroe <june@causal.agency> | 2020-11-22 00:13:50 -0500 |
commit | d98c2e778f2b6bba77ee973c10816749336b8887 (patch) | |
tree | b677a388aabf1ec0bd26b9a9d33fcef84dcfe0aa /src/bin/day04.rs | |
parent | Day 4 (diff) | |
download | aoc-d98c2e778f2b6bba77ee973c10816749336b8887.tar.gz aoc-d98c2e778f2b6bba77ee973c10816749336b8887.zip |
Day 4 part 2
Diffstat (limited to '')
-rw-r--r-- | src/bin/day04.rs | 64 |
1 files changed, 56 insertions, 8 deletions
diff --git a/src/bin/day04.rs b/src/bin/day04.rs index 9f7d0ab..c6a9709 100644 --- a/src/bin/day04.rs +++ b/src/bin/day04.rs @@ -26,7 +26,7 @@ impl FromStr for Room { } impl Room { - fn real(&self) -> bool { + fn checksum(&self) -> String { let mut letters = [ (0, 'a'), (0, 'b'), (0, 'c'), (0, 'd'), (0, 'e'), (0, 'f'), (0, 'g'), (0, 'h'), (0, 'i'), (0, 'j'), (0, 'k'), (0, 'l'), (0, 'm'), (0, 'n'), (0, 'o'), (0, 'p'), @@ -41,29 +41,71 @@ impl Room { letters.sort(); - let expected: String = letters.into_iter() + letters.into_iter() .map(|l| l.1) .take(5) - .collect(); + .collect() + } + + fn verify_checksum(&self) -> bool { + self.checksum == self.checksum() + } - expected == self.checksum + fn decrypt_name(&self) -> String { + self.name.chars() + .map(|c| { + match c { + '-' => ' ', + _ => rotate(c, self.sector_id), + } + }) + .collect() } } -fn solve(input: &str) -> u32 { +fn rotate(c: char, n: u32) -> char { + let mut c = c; + for _ in 0..n { + c = match c { + 'a' ... 'y' => (c as u8 + 1) as char, + 'z' => 'a', + _ => panic!("cannot rotate {}", c), + } + } + c +} + +fn solve1(input: &str) -> u32 { input.lines() .map(str::parse) .map(Result::unwrap) - .filter(Room::real) + .filter(Room::verify_checksum) .map(|room| room.sector_id) .sum() } +fn solve2(input: &str) -> Option<u32> { + input.lines() + .map(str::parse) + .map(Result::unwrap) + .filter(Room::verify_checksum) + .filter_map(|r| { + match r.decrypt_name().as_str() { + "northpole object storage" => Some(r.sector_id), + _ => None, + } + }) + .next() +} + fn main() { let mut input = String::new(); io::stdin().read_to_string(&mut input).unwrap(); - println!("Part 1: {}", solve(&input)); + println!("Part 1: {}", solve1(&input)); + if let Some(sector_id) = solve2(&input) { + println!("Part 2: {}", sector_id); + } } #[test] @@ -74,5 +116,11 @@ a-b-c-d-e-f-g-h-987[abcde] not-a-real-room-404[oarel] totally-real-room-200[decoy] "; - assert_eq!(1514, solve(&input[1..])); + assert_eq!(1514, solve1(&input[1..])); +} + +#[test] +fn part2() { + let room: Room = "qzmt-zixmtkozy-ivhz-343[zimth]".parse().unwrap(); + assert_eq!("very encrypted name", room.decrypt_name()); } |