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91 lines
2.8 KiB
91 lines
2.8 KiB
7 years ago
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use std::convert::TryFrom;
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use failure::*;
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use regex::Regex;
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pub fn solve(input: &str) -> Result<String, Error> {
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// let input = "s1,x3/4,pe/b";
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let moves: Vec<_> = input
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.split(',')
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.map(Move::try_from)
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.collect::<Result<_, _>>()?;
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let mut programs = (b'a'..=b'p').map(|c| c as char).collect::<Vec<_>>();
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dance(&moves, &mut programs);
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Ok(programs.iter().collect())
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}
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fn dance(moves: &[Move], programs: &mut [char]) {
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for m in moves {
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match m {
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Move::Spin(size) => {
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let len = programs.len();
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programs.rotate(len - size);
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}
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Move::Exchange(a, b) => {
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programs.swap(*a, *b);
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}
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Move::Partner(a, b) => {
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let a = programs.iter().position(|x| x == a).unwrap();
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let b = programs.iter().position(|x| x == b).unwrap();
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programs.swap(a, b);
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}
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}
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}
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}
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#[test]
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fn test_dance() {
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let moves = vec![Move::Spin(1), Move::Exchange(3, 4), Move::Partner('e', 'b')];
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let mut programs: Vec<_> = (b'a'..=b'e').map(|c| c as char).collect();
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dance(&moves, &mut programs);
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assert_eq!(programs, vec!['b', 'a', 'e', 'd', 'c']);
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}
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#[derive(Debug, Eq, PartialEq)]
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enum Move {
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Spin(usize),
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Exchange(usize, usize),
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Partner(char, char),
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}
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lazy_static! {
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static ref RE_S: Regex = { Regex::new(r"s(\d+)").unwrap() };
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static ref RE_X: Regex = { Regex::new(r"x(\d+)/(\d+)").unwrap() };
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static ref RE_P: Regex = { Regex::new(r"p(\w)/(\w)").unwrap() };
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}
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impl<'a> TryFrom<&'a str> for Move {
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type Error = Error;
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fn try_from(value: &str) -> Result<Self, Self::Error> {
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RE_S.captures(value)
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.and_then(|c| {
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let size = c.get(1).unwrap().as_str().parse().ok()?;
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Some(Move::Spin(size))
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})
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.or_else(|| {
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RE_X.captures(value).and_then(|c| {
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let a = c.get(1).unwrap().as_str().parse().ok()?;
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let b = c.get(2).unwrap().as_str().parse().ok()?;
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Some(Move::Exchange(a, b))
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})
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})
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.or_else(|| {
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RE_P.captures(value).and_then(|c| {
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let a = c.get(1).unwrap().as_str().chars().next()?;
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let b = c.get(2).unwrap().as_str().chars().next()?;
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Some(Move::Partner(a, b))
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})
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})
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.ok_or_else(|| format_err!("invalid move: {}", value))
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}
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}
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#[test]
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fn test_move_try_from() {
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assert_eq!(Move::try_from("s1").unwrap(), Move::Spin(1));
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assert_eq!(Move::try_from("x3/4").unwrap(), Move::Exchange(3, 4));
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assert_eq!(Move::try_from("pe/b").unwrap(), Move::Partner('e', 'b'));
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}
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