advent of code 2023

day1.rs

fn day1(input: &str) -> usize {
    let digits = vec!["one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];
    let digits_rev = vec!["eno", "owt", "eerht", "ruof", "evif", "xis", "neves", "thgie", "enin"];
    let values = vec!['1','2','3','4','5','6','7','8','9'];
    
    input.lines().map(|line| {
      let regular = line.chars().collect::<Vec<char>>();
      let reversed = line.chars().rev().collect::<Vec<char>>();
      let mut s = String::new();
      for (chars, digits) in vec![(regular, &digits), (reversed, &digits_rev)] {
        let first_numeric =
          chars.iter()
          .enumerate()
          .find_map(|c|
            if c.1.is_numeric() {
              Some((c.0, *c.1))
            } else {
              None
            });
        let mut first_literal: Option<(usize, char)> = None;
        let str = String::from_iter(chars);
        for (i, d) in digits.iter().enumerate() {
          if let Some(index) = str.find(d) {
            match first_literal {
              Some(e) if index < e.0 => {
                first_literal = Some((index, values[i]));
              },
              None => {
                first_literal = Some((index, values[i]));
              }
              _ => {}
            }
          }
        }
        match (first_literal, first_numeric) {
            (Some((i, a)), Some((j, b))) => if i < j {
                s.push(a);
            } else {
                s.push(b);
            },
            (Some((_, c)), _) => {
                s.push(c);
            },
            (_, Some((_, c))) => {
                s.push(c);
            },
            _ => {}
        }
      }
      s
    }).fold(0, |acc, x| acc + x.parse::<usize>().unwrap_or_default())
}