pub fn last_stone_weight(mut stones: Vec<i32>) -> i32 {
    if stones.len() == 1 {
        return *stones.get(0).unwrap();
    } else if stones.len() == 0 {
        return 0;
    }
    // sort
    stones.sort_by(|a, b| b.cmp(a));
    // remove the max twice
    let m1 = stones.remove(0);
    let m2 = stones.remove(0);
    // add result, if any
    if m1 != m2 {
        stones.push(m1 - m2);
    }
    // go again
    return last_stone_weight(stones);
}

pub fn main() {
    println!("Expected: 1");
    println!("Got: {}", last_stone_weight(vec![2, 7, 4, 1, 8, 1]));
}