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 {
6        return BinaryHeap::new();
7    }
8
9    let mut heap = iter.by_ref().take(k).collect::<BinaryHeap<_>>();
10
11    iter.for_each(|i| {
12        debug_assert_eq!(heap.len(), k);
13        // Equivalent to heap.push(min(i, heap.pop())) but more efficient.
14        // This should be done with a single `.peek_mut().unwrap()` but
15        //  `PeekMut` sifts-down unconditionally on Rust 1.46.0 and prior.
16        if *heap.peek().unwrap() > i {
17            *heap.peek_mut().unwrap() = i;
18        }
19    });
20
21    heap
22}
itertools/k_smallest.rs

itertools/
k_smallest.rs
