/**
 * [3174] Clear Digits
 */
pub struct Solution {}

// submission codes start here

impl Solution {
    pub fn clear_digits(s: String) -> String {
        let s: Vec<char> = s.chars().collect();
        let mut mark = vec![true; s.len()];

        for (i, &c) in s.iter().enumerate() {
            if !c.is_ascii_digit() {
                continue;
            }

            // 是数字
            mark[i] = false;
            let mut last = i - 1;

            while !mark[last] {
                last -= 1;
            }
            mark[last] = false;
        }

        s.iter()
            .enumerate()
            .filter_map(|(i, &c)| if mark[i] { Some(c) } else { None })
            .collect()
    }
}

// submission codes end

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_3174() {
        assert_eq!("abc".to_owned(), Solution::clear_digits("abc".to_owned()));
        assert_eq!("".to_owned(), Solution::clear_digits("cb34".to_owned()));
    }
}