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|
/// Sometimes I wake up in the morning and pretend to be a regex engine
use std::{error::Error, fs::File, io::Read};
#[derive(PartialEq, Eq, Copy, Clone, Debug)]
enum State {
Outside,
D,
O,
DoLParen,
N,
Apos,
T,
DontLParen,
M,
U,
L,
Num1,
Num2,
End,
}
struct Scanner {
state: State,
mul_enable: bool,
num1: i64,
num2: i64,
total1: i64,
total2: i64,
}
impl Scanner {
fn new() -> Self {
Self {
state: State::Outside,
mul_enable: true,
num1: 0,
num2: 0,
total1: 0,
total2: 0,
}
}
fn feed(&mut self, s: &[u8]) {
// Technically I should be feeding an "EOF" character but it's fine
// since we don't terminate on repetition
for c in s.iter().copied() {
let next_state = match self.state {
State::Outside | State::End => match c {
b'm' => State::M,
b'd' => State::D,
_ => State::Outside,
},
State::D => match c {
b'o' => State::O,
_ => State::Outside,
},
State::O => match c {
b'(' => State::DoLParen,
b'n' => State::N,
_ => State::Outside,
},
State::N => match c {
b'\'' => State::Apos,
_ => State::Outside,
},
State::Apos => match c {
b't' => State::T,
_ => State::Outside,
},
State::T => match c {
b'(' => State::DontLParen,
_ => State::Outside,
},
State::DoLParen | State::DontLParen => match c {
b')' => State::End,
_ => State::Outside,
},
State::M => match c {
b'u' => State::U,
_ => State::Outside,
},
State::U => match c {
b'l' => State::L,
_ => State::Outside,
},
State::L => match c {
b'(' => State::Num1,
_ => State::Outside,
},
State::Num1 => match c {
b',' => State::Num2,
_ if c.is_ascii_digit() => State::Num1,
_ => State::Outside,
},
State::Num2 => match c {
b')' => State::End,
_ if c.is_ascii_digit() => State::Num2,
_ => State::Outside,
},
};
match (self.state, next_state) {
(State::L, State::Num1) => self.num1 = 0,
(State::Num1, State::Num2) => self.num2 = 0,
(State::DoLParen, State::End) => self.mul_enable = true,
(State::DontLParen, State::End) => self.mul_enable = false,
(State::Num2, State::End) => {
let m = self.num1 * self.num2;
self.total1 += m;
if self.mul_enable {
self.total2 += m;
}
}
(State::Num1, State::Num1) => {
self.num1 *= 10;
self.num1 += char::from(c).to_digit(10).unwrap() as i64;
}
(State::Num2, State::Num2) => {
self.num2 *= 10;
self.num2 += char::from(c).to_digit(10).unwrap() as i64;
}
_ => (),
}
self.state = next_state;
}
}
fn totals(&self) -> (i64, i64) {
(self.total1, self.total2)
}
}
fn main() -> Result<(), Box<dyn Error>> {
let mut f = File::open("input/3")?;
let mut buf = [0; 8 * 1024];
let mut scanner = Scanner::new();
loop {
let n = f.read(&mut buf)?;
if n == 0 {
break;
};
scanner.feed(&buf[..n]);
}
let (p1, p2) = scanner.totals();
println!("{p1}\n{p2}");
Ok(())
}
|
