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author | June McEnroe <june@causal.agency> | 2016-12-17 01:25:18 -0500 |
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committer | June McEnroe <june@causal.agency> | 2020-11-22 00:14:25 -0500 |
commit | 655847206033a875daef99be01fb5a04946c2a25 (patch) | |
tree | 1aac078b5efdc0e83662060f200169d287915448 /src/bin/day16.rs | |
parent | Day 15 part 2 (diff) | |
download | aoc-655847206033a875daef99be01fb5a04946c2a25.tar.gz aoc-655847206033a875daef99be01fb5a04946c2a25.zip |
Day 16
Diffstat (limited to 'src/bin/day16.rs')
-rw-r--r-- | src/bin/day16.rs | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/src/bin/day16.rs b/src/bin/day16.rs new file mode 100644 index 0000000..21648b2 --- /dev/null +++ b/src/bin/day16.rs @@ -0,0 +1,50 @@ +use std::io::{self, Read}; + +fn fill_disk(initial_state: &str, len: usize) -> String { + let mut state = String::from(initial_state); + while state.len() < len { + let mut b: Vec<u8> = state.bytes() + .map(|b| { + match b { + b'0' => b'1', + b'1' => b'0', + _ => b, + } + }) + .collect(); + b.reverse(); + let b = String::from_utf8(b).unwrap(); + state.push('0'); + state.push_str(&b); + } + state.truncate(len); + state +} + +fn checksum(data: &str) -> String { + let mut sum = String::from(data); + while sum.len() % 2 == 0 { + sum = sum.as_bytes() + .chunks(2) + .map(|c| if c[0] == c[1] { '1' } else { '0' }) + .collect(); + } + sum +} + +fn solve(len: usize, initial_state: &str) -> String { + let data = fill_disk(initial_state, len); + checksum(&data) +} + +fn main() { + let mut input = String::new(); + io::stdin().read_to_string(&mut input).unwrap(); + + println!("Part 1: {}", solve(272, input.trim())); +} + +#[test] +fn part1() { + assert_eq!("01100", solve(20, "10000")); +} |