Rust feat. pest

No Zalgo here! I wasted a huge amount of time by not noticing that the second part's example input was different - my code worked fine but my test failed 🤦‍♂️

pest.rs is lovely, although part two made my PEG a bit ugly.

part1    =  { SOI ~ (mul_expr | junk)+ ~ EOI }
part2    =  { (enabled | disabled)+ ~ EOI }
mul_expr =  { "mul(" ~ number ~ "," ~ number ~ ")" }
number   =  { ASCII_DIGIT{1,3} }
junk     = _{ ASCII }
on       = _{ "do()" }
off      = _{ "don't()" }
enabled  = _{ (SOI | on) ~ (!(off) ~ (mul_expr | junk))+ }
disabled = _{ off ~ (!(on) ~ junk)+ }

use std::fs;

use color_eyre::eyre;
use pest::Parser;
use pest_derive::Parser;

#[derive(Parser)]
#[grammar = "memory.pest"]
pub struct MemoryParser;

fn parse(input: &str, rule: Rule) -> eyre::Result<usize> {
    let sum = MemoryParser::parse(rule, input)?
        .next()
        .expect("input must be ASCII")
        .into_inner()
        .filter(|pair| pair.as_rule() == Rule::mul_expr)
        .map(|pair| {
            pair.into_inner()
                .map(|num| num.as_str().parse::<usize>().unwrap())
                .product::<usize>()
        })
        .sum();
    Ok(sum)
}

fn part1(filepath: &str) -> eyre::Result<usize> {
    let input = fs::read_to_string(filepath)?;
    parse(&input, Rule::part1)
}

fn part2(filepath: &str) -> eyre::Result<usize> {
    let input = fs::read_to_string(filepath)?;
    parse(&input, Rule::part2)
}

fn main() -> eyre::Result<()> {
    color_eyre::install()?;

    let part1 = part1("d03/input.txt")?;
    let part2 = part2("d03/input.txt")?;
    println!("Part 1: {part1}\nPart 2: {part2}");
    Ok(())
}

I did part 2 live with the python interactive shell. I deleted all the stuff where I was just exploring ideas.

part 1:

import re

def multiply_and_add(data: "str") -> int:
    digit_matches = re.findall(r"mul\(\d{0,3},\d{0,3}\)", data)
    result = 0
    for _ in digit_matches:
        first = _.split("(")[1].split(")")[0].split(",")[0]
        second = _.split("(")[1].split(")")[0].split(",")[1]
        result += int(first) * int(second)

    return result

with open("input") as file:
    data = file.read()


answer = multiply_and_add(data)
print(answer)

part 2:

Python 3.11.2 (main, Aug 26 2024, 07:20:54) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import solution2
<re.Match object; span=(647, 651), match='do()'>
>>> from solution2 import *
>>> split_on_dont = data.split("don't()")
>>> valid = []
>>> valid.append(split_on_dont[0])
>>> for substring in split_on_dont[1:]:
...     subsubstrings = substring.split("do()", maxsplit=1)
...     for subsubstring in subsubstrings[1:]:
...             valid.append(subsubstring)
...
>>> answer = 0
>>> for _ in valid:
...     answer += multiply_and_add(_)
...
>>> answer
103811193