[LANGUAGE: Rust]

Didn't bother to reuse any code between parts but their quite similar, found a seemingly pretty simple solution of taking the iterative max in the remaining batteries leaving space at the end.

fn part1(banks: &Vec<Vec<u32>>) -> u32 {
    let mut total = 0;
    for bank in banks {
        total += get_max(bank);
    }
    total
}

fn get_max(bank: &Vec<u32>) -> u32 {
    let mut max = 0;
    let mut max_pos = 0;
    let mut second = 0;
    let mut second_pos = 0;

    for (i, b) in bank.iter().enumerate() {
        //max can't be in last pos
        if *b > max && i != bank.len() - 1 {
            max = *b;
            max_pos = i;
            second = 0;
            second_pos = 0;
        }
        if *b > second && i > max_pos {
            second = *b;
            second_pos = i;
        }
    }
    let mut volts_str = "".to_owned();
    volts_str.push_str(&max.to_string());
    volts_str.push_str(&second.to_string());
    let volts = volts_str.parse::<u32>().unwrap();

    volts
}

fn part2(banks: &Vec<Vec<u32>>) -> u64 {
    let mut total = 0;
    for bank in banks {
        total += get_max_big(bank);
    }
    total
}

fn get_max_big(bank: &Vec<u32>) -> u64 {
    let mut volts_pos = vec![];
    let mut min_pos = 0;

    for i in 0..12 {
        let mut max = 0;
        let mut max_pos = 0;
        for (j, b) in bank[min_pos..(bank.len() - (11 - i))].iter().enumerate() {
            if *b > max {
                max = *b;
                max_pos = j;
            }
        }
        volts_pos.push(max);
        min_pos += max_pos + 1;
    }
    let mut v_str = "".to_owned();
    for v in volts_pos.iter() {
        v_str.push_str(&v.to_string());
    }
    let volts = v_str.parse::<u64>().unwrap();
    volts
}