aoc-2023-3.rs

use std::collections::{HashMap, HashSet};

use crate::util::Grid;

// just pretend you know what Grid does
pub fn part_1(input: &str) -> u32 {
    let grid = Grid::create(input);
    let mut sum = 0;

    for y in 0..grid.height() {
        let mut curr = 0;
        let mut is_part = false;

        for x in 0..grid.width() {
            if let Some(n) = grid.at(x, y).as_digit() {
                curr = curr * 10 + n;

                if grid.at(x, y).count_adjacent(|c| !c.is_ascii_digit() && c != '.') > 0 {
                    is_part = true;
                }
            } else {
                if is_part { sum += curr; }

                is_part = false;
                curr = 0;
            }
        } 
    }

    sum
}

pub fn part_2(input: &str) -> u64 {
    let grid = Grid::create(input);
    let mut entries = HashMap::new();
    
    for y in 0..grid.height() {
        let mut touching = HashSet::new();
        let mut curr = 0;

        for x in 0..=grid.width() {
            if let Some(n) = grid.at(x, y).as_digit() {
                curr = curr * 10 + n as u64;

                grid.at(x, y).for_adjacent(|c, i, j| {
                    if c == '*' { touching.insert((i, j)); }
                });
            } else {
                touching.iter().for_each(|(i, j)| {
                    entries.entry((*i, *j)).or_insert(Vec::new()).push(curr);
                });

                curr = 0;
                touching.clear();
            }
        }
    }

    entries.values().filter(|v| v.len() == 2).map(|v| v[0] * v[1]).sum()
}