21 lines
669 B
Rust
21 lines
669 B
Rust
use alloc::collections::BinaryHeap;
|
|
use core::cmp::Ord;
|
|
|
|
pub(crate) fn k_smallest<T: Ord, I: Iterator<Item = T>>(mut iter: I, k: usize) -> BinaryHeap<T> {
|
|
if k == 0 { return BinaryHeap::new(); }
|
|
|
|
let mut heap = iter.by_ref().take(k).collect::<BinaryHeap<_>>();
|
|
|
|
iter.for_each(|i| {
|
|
debug_assert_eq!(heap.len(), k);
|
|
// Equivalent to heap.push(min(i, heap.pop())) but more efficient.
|
|
// This should be done with a single `.peek_mut().unwrap()` but
|
|
// `PeekMut` sifts-down unconditionally on Rust 1.46.0 and prior.
|
|
if *heap.peek().unwrap() > i {
|
|
*heap.peek_mut().unwrap() = i;
|
|
}
|
|
});
|
|
|
|
heap
|
|
}
|