itertools/
k_smallest.rs

1use alloc::collections::BinaryHeap;
2use core::cmp::Ord;
3
4pub(crate) fn k_smallest<T: Ord, I: Iterator<Item = T>>(mut iter: I, k: usize) -> BinaryHeap<T> {
5    if k == 0 { return BinaryHeap::new(); }
6
7    let mut heap = iter.by_ref().take(k).collect::<BinaryHeap<_>>();
8
9    iter.for_each(|i| {
10        debug_assert_eq!(heap.len(), k);
11        // Equivalent to heap.push(min(i, heap.pop())) but more efficient.
12        // This should be done with a single `.peek_mut().unwrap()` but
13        //  `PeekMut` sifts-down unconditionally on Rust 1.46.0 and prior.
14        if *heap.peek().unwrap() > i {
15            *heap.peek_mut().unwrap() = i;
16        }
17    });
18
19    heap
20}
itertools/k_smallest.rs

itertools/
k_smallest.rs
