pub fn split_from(min: usize, max: usize, x: usize) -> Vec<Vec<usize>> {
    if min > x || x > max {
        return Vec::new();
    }
    let x_lower = x.checked_sub(1).unwrap_or(min);
    let x_upper = (x + 1).min(max);
    let lower_range = if x_lower != min {
        (min..=x_lower).rev().collect()
    } else {
        Vec::new()
    };
    let upper_range = if x_upper != max {
        (x_upper..=max).collect()
    } else {
        Vec::new()
    };
    vec![lower_range, upper_range]
}

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

    #[test]
    fn split_test() {
        assert_eq!(split_from(0, 6, 2), vec![vec![1, 0], vec![3, 4, 5, 6]]);

        assert_eq!(split_from(0, 6, 0), vec![vec![], vec![1, 2, 3, 4, 5, 6]]);

        assert_eq!(split_from(0, 6, 6), vec![vec![5, 4, 3, 2, 1, 0], vec![]]);
    }
}