use std::io::{self, Read}; #[derive(Clone, Copy)] enum Operation { SwapPosition(usize, usize), SwapLetter(u8, u8), RotateLeft(usize), RotateRight(usize), RotateLetter(u8), Reverse(usize, usize), Move(usize, usize), } impl Operation { fn apply(self, slice: &mut [u8]) { match self { Operation::SwapPosition(i, j) => slice.swap(i, j), Operation::SwapLetter(a, b) => { let i = slice.iter().position(|&x| x == a).unwrap(); let j = slice.iter().position(|&x| x == b).unwrap(); slice.swap(i, j); }, Operation::RotateLeft(n) => { let n = n % slice.len(); slice[0..n].reverse(); slice[n..].reverse(); slice.reverse(); }, Operation::RotateRight(n) => { let n = n % slice.len(); slice.reverse(); slice[0..n].reverse(); slice[n..].reverse(); }, Operation::RotateLetter(a) => { let mut n = 1 + slice.iter().position(|&x| x == a).unwrap(); if n >= 5 { n += 1 } n %= slice.len(); slice.reverse(); slice[0..n].reverse(); slice[n..].reverse(); }, Operation::Reverse(i, j) => slice[i..(j + 1)].reverse(), Operation::Move(i, j) if i < j => { let a = slice[i]; for k in i..j { slice[k] = slice[k + 1]; } slice[j] = a; }, Operation::Move(i, j) => { let a = slice[i]; for k in (j..i).rev() { slice[k + 1] = slice[k]; } slice[j] = a; }, } } } impl<'a> From<&'a str> for Operation { fn from(s: &'a str) -> Self { let mut iter = s.split_whitespace(); match (iter.next().unwrap(), iter.next().unwrap()) { ("swap", "position") => Operation::SwapPosition( iter.next().unwrap().parse().unwrap(), iter.nth(2).unwrap().parse().unwrap(), ), ("swap", "letter") => Operation::SwapLetter( iter.next().unwrap().as_bytes()[0], iter.nth(2).unwrap().as_bytes()[0], ), ("rotate", "left") => Operation::RotateLeft(iter.next().unwrap().parse().unwrap()), ("rotate", "right") => Operation::RotateRight(iter.next().unwrap().parse().unwrap()), ("rotate", "based") => Operation::RotateLetter(iter.nth(4).unwrap().as_bytes()[0]), ("reverse", _) => Operation::Reverse( iter.next().unwrap().parse().unwrap(), iter.nth(1).unwrap().parse().unwrap(), ), ("move", _) => Operation::Move( iter.next().unwrap().parse().unwrap(), iter.nth(2).unwrap().parse().unwrap(), ), (x, y) => panic!("invalid operation {} {}", x, y), } } } fn solve(password: &str, input: &str) -> String { let mut password = password.as_bytes().to_owned(); for operation in input.lines().map(Operation::from) { operation.apply(&mut password); } String::from_utf8(password).unwrap() } fn main() { let mut input = String::new(); io::stdin().read_to_string(&mut input).unwrap(); println!("Part 1: {}", solve("abcdefgh", &input)); } #[test] fn part1() { let input = " swap position 4 with position 0 swap letter d with letter b reverse positions 0 through 4 rotate left 1 step move position 1 to position 4 move position 3 to position 0 rotate based on position of letter b rotate based on position of letter d "; assert_eq!("decab", solve("abcde", input.trim())); }