1 use alloc::collections::BinaryHeap;
2 use core::cmp::Ord;
3 
k_smallest<T: Ord, I: Iterator<Item = T>>(mut iter: I, k: usize) -> BinaryHeap<T>4 pub(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 }
21