dat2

use std::iter::{Iterator, Peekable};

// this struct lets you create an iterator from 2 sub iterators, and it will 
// automatically return the interleaved, sorted results without much cost
struct OrderedIterator<I: Ord + Clone, P: Iterator<Item = I>> {
    first: Peekable<P>,
    second: Peekable<P>,
    pop_from: usize,
    first_empty: bool,
    second_empty: bool,