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use std::io::{self, Read};
enum Chunk<'a> {
Literal(&'a str),
Repeat(u32, &'a str),
Recursive(u32, Vec<Chunk<'a>>),
}
impl<'a> Chunk<'a> {
fn len(&self) -> usize {
match *self {
Chunk::Literal(s) => s.len(),
Chunk::Repeat(n, s) => n as usize * s.len(),
Chunk::Recursive(n, ref cs) => n as usize * cs.iter().map(Chunk::len).sum::<usize>(),
}
}
fn parse(s: &'a str) -> Result<(Self, &'a str), ()> {
if s.starts_with('(') {
let mut iter = s[1..].splitn(3, |ch| ch == 'x' || ch == ')');
let len = iter.next().ok_or(())?.parse().map_err(|_| ())?;
let repeat = iter.next().ok_or(())?.parse().map_err(|_| ())?;
let (data, rest) = iter.next().ok_or(())?.split_at(len);
Ok((Chunk::Repeat(repeat, data), rest))
} else {
let paren = s.find('(').unwrap_or(s.len());
Ok((Chunk::Literal(&s[..paren]), &s[paren..]))
}
}
fn parse_v2(s: &'a str) -> Result<(Self, &'a str), ()> {
if s.starts_with('(') {
let mut iter = s[1..].splitn(3, |ch| ch == 'x' || ch == ')');
let len = iter.next().ok_or(())?.parse().map_err(|_| ())?;
let repeat = iter.next().ok_or(())?.parse().map_err(|_| ())?;
let (mut data, rest) = iter.next().ok_or(())?.split_at(len);
let mut chunks = Vec::new();
while !data.is_empty() {
let (chunk, data_rest) = Chunk::parse_v2(data)?;
chunks.push(chunk);
data = data_rest;
}
Ok((Chunk::Recursive(repeat, chunks), rest))
} else {
let paren = s.find('(').unwrap_or(s.len());
Ok((Chunk::Literal(&s[..paren]), &s[paren..]))
}
}
}
struct File<'a> {
chunks: Vec<Chunk<'a>>,
}
impl<'a> File<'a> {
fn len(&self) -> usize {
self.chunks.iter().map(Chunk::len).sum()
}
fn parse(mut s: &'a str) -> Result<Self, ()> {
let mut chunks = Vec::new();
while !s.is_empty() {
let (chunk, rest) = Chunk::parse(s)?;
chunks.push(chunk);
s = rest;
}
Ok(File { chunks: chunks })
}
fn parse_v2(mut s: &'a str) -> Result<Self, ()> {
let mut chunks = Vec::new();
while !s.is_empty() {
let (chunk, rest) = Chunk::parse_v2(s)?;
chunks.push(chunk);
s = rest;
}
Ok(File { chunks: chunks })
}
}
fn solve1(input: &str) -> usize {
let file = File::parse(input).unwrap();
file.len()
}
fn solve2(input: &str) -> usize {
let file = File::parse_v2(input).unwrap();
file.len()
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve1(&input));
println!("Part 2: {}", solve2(&input));
}
#[test]
fn part1() {
assert_eq!(6, solve1("ADVENT"));
assert_eq!(7, solve1("A(1x5)BC"));
assert_eq!(9, solve1("(3x3)XYZ"));
assert_eq!(11, solve1("A(2x2)BCD(2x2)EFG"));
assert_eq!(6, solve1("(6x1)(1x3)A"));
assert_eq!(18, solve1("X(8x2)(3x3)ABCY"));
}
#[test]
fn part2() {
assert_eq!(9, solve2("(3x3)XYZ"));
assert_eq!(20, solve2("X(8x2)(3x3)ABCY"));
assert_eq!(241920, solve2("(27x12)(20x12)(13x14)(7x10)(1x12)A"));
assert_eq!(445, solve2("(25x3)(3x3)ABC(2x3)XY(5x2)PQRSTX(18x9)(3x2)TWO(5x7)SEVEN"));
}
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