11.rs

const INPUT: &str = include_str!("11.txt");

fn main() { one(); two(); }

fn one() {
    // TODO FALSE
    let mut result = increment(INPUT.into());

    let mut todo = 0;
    while !(
    has_consecutive_letters(&result, b' ', 1)
    && !['i', 'o', 'l'].iter().any(|c| result.contains(*c))
    && has_two_double_letters(&result, ' ', 0)
) {
        // TODO
        todo += 1;
        println!("{todo}");
        result = increment(result);
    }

    print!("11.1: {result}\t\t");
}

fn two() {
    todo!()
    let result = 0;
    println!("11.2: {result}");
}

fn has_consecutive_letters(input: &str, prev: u8, series: u8) -> bool {
    if series == 3 { return true; }

    match input.chars().next() {
        Some(c) if c as u8 == prev + 1 => has_consecutive_letters(&input[1..], c as u8, series + 1),
        Some(c) => has_consecutive_letters(&input[1..], c as u8, 1),
        None => false
    }
}

fn has_two_double_letters(input: &str, prev: char, count: u8) -> bool {
    if count == 2 { return true; }

    match input.chars().next() {
        Some(c) if c == prev => has_two_double_letters(&input[1..], ' ', count + 1),
        Some(c) => has_two_double_letters(&input[1..], c, count),
        None => false
    }
}

fn increment(input: String) -> String {
    real_increment(input.chars().rev().collect()).chars().rev().collect()
}

fn real_increment(input: String) -> String {
    match input.chars().next().unwrap() {
        'z' => format!("a{}", increment(input[1..].into())),
        other => format!("{}{}", (other as u8 + 1) as char, &input[1..]),
    }
}