use crate::common::array_stack::ArrayStack;
use crate::input::{Input, on_error};
pub fn solve(input: &Input) -> Result<u32, String> {
let mut page_ordering = [0_u128; 100];
let mut sum = 0;
for line in input.text.lines() {
if let Some((before, after)) = line.split_once('|') {
let before = parse_page(before)?;
let after = parse_page(after)?;
page_ordering[before as usize] |= 1 << (after as u128);
} else if !line.is_empty() {
let mut parts = ArrayStack::<100, u8>::new();
for part in line.split(',') {
let part = part.parse::<u8>().map_err(|_| on_error())?;
parts.push(part)?;
}
let mut valid = true;
for (idx, &before) in parts.slice().iter().enumerate() {
for &after in parts.slice().iter().skip(idx + 1) {
if page_ordering[before as usize] & (1 << (after as u128)) == 0 {
valid = false;
}
}
}
sum += match (input.is_part_one(), valid) {
(true, true) => parts.elements[parts.len() / 2] as u32,
(false, false) => {
let l = parts.slice_mut();
l.sort_unstable_by(|&a, &b| {
0.cmp(&(page_ordering[a as usize] & (1 << (b as u128))))
});
l[l.len() / 2] as u32
}
_ => 0,
};
}
}
Ok(sum)
}
fn parse_page(s: &str) -> Result<u8, String> {
let n = s.parse::<u8>().map_err(|_| on_error())?;
if n >= 100 {
return Err(format!("Too big page number: {n}"));
}
Ok(n)
}
#[test]
pub fn tests() {
let test_input = "47|53
97|13
97|61
97|47
75|29
61|13
75|53
29|13
97|29
53|29
61|53
97|53
61|29
47|13
75|47
97|75
47|61
75|61
47|29
75|13
53|13
75,47,61,53,29
97,61,53,29,13
75,29,13
75,97,47,61,53
61,13,29
97,13,75,29,47";
test_part_one_no_allocations!(test_input => 143);
test_part_two_no_allocations!(test_input => 123);
let real_input = include_str!("day05_input.txt");
test_part_one_no_allocations!(real_input => 6612);
test_part_two_no_allocations!(real_input => 4944);
}