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use std::io::{self, Read};
use std::str::FromStr;
struct Chunk {
data: String,
repeat: u32,
}
impl Chunk {
fn len(&self) -> usize {
self.data.len() * self.repeat as usize
}
fn parse(s: &str) -> Result<(Self, &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);
let chunk = Chunk {
data: data.to_owned(),
repeat: repeat,
};
Ok((chunk, rest))
} else {
let paren = s.find('(').unwrap_or(s.len());
let chunk = Chunk {
data: s[..paren].to_owned(),
repeat: 1,
};
let rest = &s[paren..];
Ok((chunk, rest))
}
}
}
struct File {
chunks: Vec<Chunk>,
}
impl File {
fn len(&self) -> usize {
self.chunks.iter().map(Chunk::len).sum()
}
}
impl FromStr for File {
type Err = ();
fn from_str(mut s: &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 solve(input: &str) -> usize {
let file: File = input.parse().unwrap();
file.len()
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve(&input));
}
#[test]
fn part1() {
assert_eq!(6, solve("ADVENT"));
assert_eq!(7, solve("A(1x5)BC"));
assert_eq!(9, solve("(3x3)XYZ"));
assert_eq!(11, solve("A(2x2)BCD(2x2)EFG"));
assert_eq!(6, solve("(6x1)(1x3)A"));
assert_eq!(18, solve("X(8x2)(3x3)ABCY"));
}
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