year2015/
day04.rs

1use std::sync::atomic::{AtomicU32, Ordering};
2use utils::md5;
3use utils::prelude::*;
4
5/// Finding MD5 hashes with leading zeroes.
6///
7/// See [`md5::find_hash_with_appended_count()`].
8#[derive(Clone, Debug)]
9pub struct Day04<'a> {
10    prefix: &'a str,
11}
12
13impl<'a> Day04<'a> {
14    pub fn new(input: &'a str, _: InputType) -> Result<Self, InputError> {
15        Ok(Self { prefix: input })
16    }
17
18    #[must_use]
19    pub fn part1(&self) -> u32 {
20        self.find_hash_matching(0xFFFF_F000)
21    }
22
23    #[must_use]
24    pub fn part2(&self) -> u32 {
25        self.find_hash_matching(0xFFFF_FF00)
26    }
27
28    fn find_hash_matching(&self, mask: u32) -> u32 {
29        let result = AtomicU32::new(u32::MAX);
30
31        md5::find_hash_with_appended_count(self.prefix, 0, |i, [a, ..]| {
32            if i > 0 && a & mask == 0 {
33                result.fetch_min(i, Ordering::AcqRel);
34                true
35            } else {
36                false
37            }
38        });
39
40        result.load(Ordering::Acquire)
41    }
42}
43
44examples!(Day04<'_> -> (u32, u32) [
45    {input: "abcdef", part1: 609043},
46    {input: "pqrstuv", part1: 1048970},
47]);
year2015/day04.rs

year2015/
day04.rs
