AdventOfCode2023/src/bin/day4.rs

use aoc2023_niels_overkamp::common::{self, AOCResult};
use nom::character::complete::multispace1;
use nom::sequence::{preceded, terminated, tuple};
use nom::bytes::complete::tag;
use nom::character::complete::u32 as u32_parser;
use nom::error::convert_error;
use nom::multi::separated_list0;
use nom::combinator::all_consuming;
use nom::Finish;
use std::collections::HashSet;


const DAY: &str = "day4";

fn main() -> Result<(), Box<dyn std::error::Error>> {
    common::run(DAY, &run)
}

pub fn run(input: &Vec<String>) -> AOCResult {
    let id_parser = preceded(tuple((tag("Card"), multispace1)), terminated(u32_parser, tuple((tag(":"), multispace1))));
    let numbers_parser_gen = || separated_list0(multispace1, u32_parser);
    let mut card_parser = all_consuming(tuple((
        id_parser, 
        terminated(
            numbers_parser_gen(), 
            tuple((tag(" |"), multispace1))), 
        numbers_parser_gen())));
        
    let mut copy_counter = vec![];
    let mut sum = 0;
    for line in input.iter() {
        let (_, (id, win_numbers, my_numbers)) = card_parser(line.as_str())
            .finish()
            .map_err(|e| convert_error(line.as_str(), e))?;
        let win_numbers = HashSet::<_>::from_iter(win_numbers.into_iter());
        let my_numbers = HashSet::<_>::from_iter(my_numbers.into_iter());
        
        let id = id as usize;
        let win_count = win_numbers.intersection(&my_numbers).count();
        copy_counter.resize(copy_counter.len().max(id+win_count), 1);
        let copy_count = copy_counter[id - 1];
        if win_count > 0 {
            sum += 1 << (win_count - 1);
            
            for id in id..id+win_count {
                copy_counter[id] += copy_count;
            }
        }
    }
            

    Ok([Some(sum.to_string()), Some(copy_counter.into_iter().sum::<u32>().to_string())])
}

#[test]
pub fn test_day4() {
    assert!(common::run_test(DAY, &run))
}