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day08.rs
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day08.rs
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//! # I Heard You Like Registers
//!
//! Computes both parts in a single pass.
use crate::util::hash::*;
use crate::util::iter::*;
use crate::util::parse::*;
type Input = (i32, i32);
pub fn parse(input: &str) -> Input {
let mut registers = FastMap::new();
let mut part_two = 0;
for [a, b, c, _, e, f, g] in input.split_ascii_whitespace().chunk::<7>() {
let first = *registers.entry(e).or_insert(0);
let second: i32 = g.signed();
let predicate = match f {
"==" => first == second,
"!=" => first != second,
">=" => first >= second,
"<=" => first <= second,
">" => first > second,
"<" => first < second,
_ => unreachable!(),
};
if predicate {
let third = registers.entry(a).or_insert(0);
let fourth: i32 = c.signed();
match b {
"inc" => *third += fourth,
"dec" => *third -= fourth,
_ => unreachable!(),
}
part_two = part_two.max(*third);
}
}
let part_one = *registers.values().max().unwrap();
(part_one, part_two)
}
pub fn part1(input: &Input) -> i32 {
input.0
}
pub fn part2(input: &Input) -> i32 {
input.1
}