Advent of Rust // Day 6

//

Easy one. I still haven’t figured out why Rust sometimes can not infer types, like with the hash set below.

fn position_after_unique_characters(input: &str, len: usize) -> Result<usize, String> {  
    if len > input.len() {  
        return Err(format!("String '{input}' is shorter than {len} characters"));  
    }  
  
    for index in 0..input.len() - len {  
        let chars: HashSet<char> = HashSet::from_iter((&input[index..index + len]).chars());  
  
        if chars.len() == len as usize {  
            return Ok(index + len);  
        }  
    }  
  
    return Err(format!("String '{input}' does not contain a series of {len} unique characters"));  
}  
  
fn main() {  
    let input = fs::read_to_string("input/day06.txt").unwrap();  
  
    println!("Part One: {}", position_after_unique_characters(&input, 4).unwrap());  
    println!("Part Two: {}", position_after_unique_characters(&input, 14).unwrap());  
}

If you’ve been following my little series, you might have noticed that there finally is some error handling. Until now, I only panic’d or not giving a fuck. It’s the first shot, so there’s probably room for improvement. Testing for errors was straightforward:

#[test]  
fn no_unique_characters() {  
    assert_eq!(  
        "String 'aaaa' does not contain a series of 2 unique characters",  
        position_after_unique_characters("aaaa", 2).unwrap_err()  
    );  
}  
  
#[test]  
fn input_is_shorter_than_length() {  
    assert_eq!(  
        "String 'ab' is shorter than 3 characters",  
        position_after_unique_characters("ab", 3).unwrap_err()  
    );  
}

The full source and solutions for the others puzzles of Advent of Code can be found in my GitHub repository.

See also in Advent of Rust

Comments

You can leave a comment by replying to this post on Mastodon.