aoc/year2018/
day02.rs

1//! # Inventory Management System
2use crate::util::hash::*;
3
4pub fn parse(input: &str) -> Vec<&[u8]> {
5    input.lines().map(str::as_bytes).collect()
6}
7
8pub fn part1(input: &[&[u8]]) -> u32 {
9    let mut twos = 0;
10    let mut threes = 0;
11
12    for &id in input {
13        // Ids are lowercase ASCII only with cardinality of 26.
14        let mut freq = [0_u8; 26];
15
16        for &b in id {
17            freq[(b - b'a') as usize] += 1;
18        }
19
20        twos += freq.contains(&2) as u32;
21        threes += freq.contains(&3) as u32;
22    }
23
24    twos * threes
25}
26
27pub fn part2(input: &[&[u8]]) -> String {
28    let width = input[0].len();
29    let mut seen = FastSet::with_capacity(input.len());
30
31    // Use a set to check for duplicates by comparing the prefix and suffix of IDs excluding one
32    // column at a time.
33    for column in 0..width {
34        for &id in input {
35            let pair @ (prefix, suffix) = (&id[..column], &id[column + 1..]);
36
37            if !seen.insert(pair) {
38                // Convert to String
39                return prefix.iter().chain(suffix).copied().map(char::from).collect();
40            }
41        }
42
43        seen.clear();
44    }
45
46    unreachable!()
47}
aoc/year2018/day02.rs

aoc/year2018/
day02.rs
