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use std::io::{self, Read};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum State {
Group,
Garbage,
Ignore,
}
use self::State::*;
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Machine(State, u32);
impl Machine {
fn next(self, input: char) -> Self {
match (self.0, input) {
(Ignore, _) => Machine(Garbage, self.1),
(Garbage, '!') => Machine(Ignore, self.1),
(Garbage, '>') => Machine(Group, self.1),
(Garbage, _) => self,
(Group, '<') => Machine(Garbage, self.1),
(Group, '{') => Machine(Group, self.1 + 1),
(Group, '}') => Machine(Group, self.1 - 1),
(Group, ',') => self,
_ => unimplemented!(),
}
}
}
fn solve1(input: &str) -> u32 {
let mut score = 0;
let mut state = Machine(Group, 0);
for c in input.chars() {
let next = state.next(c);
if next.1 > state.1 {
score += next.1;
}
state = next;
}
score
}
fn solve2(input: &str) -> u32 {
let mut garbage = 0;
let mut state = Machine(Group, 0);
for c in input.chars() {
let next = state.next(c);
if next == state && state.0 == Garbage {
garbage += 1;
}
state = next;
}
garbage
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve1(input.trim()));
println!("Part 2: {}", solve2(input.trim()));
}
#[test]
fn part1() {
assert_eq!(1, solve1("{}"));
assert_eq!(6, solve1("{{{}}}"));
assert_eq!(5, solve1("{{},{}}"));
assert_eq!(16, solve1("{{{},{},{{}}}}"));
assert_eq!(1, solve1("{<a>,<a>,<a>,<a>}"));
assert_eq!(9, solve1("{{<ab>},{<ab>},{<ab>},{<ab>}}"));
assert_eq!(9, solve1("{{<!!>},{<!!>},{<!!>},{<!!>}}"));
assert_eq!(3, solve1("{{<a!>},{<a!>},{<a!>},{<ab>}}"));
}
#[test]
fn part2() {
assert_eq!(0, solve2("<>"));
assert_eq!(17, solve2("<random characters>"));
assert_eq!(3, solve2("<<<<>"));
assert_eq!(2, solve2("<{!>}>"));
assert_eq!(0, solve2("<!!>"));
assert_eq!(0, solve2("<!!!>>"));
assert_eq!(10, solve2("<{o\"i!a,<{i<a>"));
}
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