From 3037ee1443a892a1c10b4d232e66c3b478d3d54b Mon Sep 17 00:00:00 2001 From: June McEnroe Date: Sat, 23 Dec 2017 19:42:36 -0500 Subject: Day 14 --- 2017/input/day14.txt | 1 + 2017/src/bin/day14.rs | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 54 insertions(+) create mode 100644 2017/input/day14.txt create mode 100644 2017/src/bin/day14.rs (limited to '2017') diff --git a/2017/input/day14.txt b/2017/input/day14.txt new file mode 100644 index 0000000..9d903be --- /dev/null +++ b/2017/input/day14.txt @@ -0,0 +1 @@ +jzgqcdpd \ No newline at end of file diff --git a/2017/src/bin/day14.rs b/2017/src/bin/day14.rs new file mode 100644 index 0000000..400a29a --- /dev/null +++ b/2017/src/bin/day14.rs @@ -0,0 +1,53 @@ +use std::io::{self, Read}; + +fn reverse(ring: &mut Vec, index: usize, len: usize) { + for i in 0..(len / 2) { + let a = (index + i) % ring.len(); + let b = (index + len - 1 - i) % ring.len(); + let x = ring[a]; + ring[a] = ring[b]; + ring[b] = x; + } +} + +fn hash(input: &str) -> Vec { + let mut ring: Vec<_> = (0..256).collect(); + let mut index = 0; + let mut skip = 0; + + let mut lens: Vec<_> = input.as_bytes().to_vec(); + lens.extend(&[17, 31, 73, 47, 23]); + + for _ in 0..64 { + for len in lens.iter().cloned() { + reverse(&mut ring, index, len as usize); + index += len as usize + skip; + index %= ring.len(); + skip += 1; + } + } + + ring.chunks(16) + .map(|chunk| chunk.iter().fold(0, |a, b| a ^ b)) + .map(|x| x as u8) + .collect() +} + +fn solve1(input: &str) -> u32 { + (0..128) + .map(|i| hash(&format!("{}-{}", input, i))) + .map(|h| h.into_iter().map(u8::count_ones).sum::()) + .sum() +} + +fn main() { + let mut input = String::new(); + io::stdin().read_to_string(&mut input).unwrap(); + + println!("Part 1: {}", solve1(input.trim())); +} + +#[test] +fn part1() { + assert_eq!(8108, solve1("flqrgnkx")); +} -- cgit 1.4.1