diff --git a/library/alloc/src/collections/binary_heap/mod.rs b/library/alloc/src/collections/binary_heap/mod.rs index 97aafbc7b6994..4ddfcde57280e 100644 --- a/library/alloc/src/collections/binary_heap/mod.rs +++ b/library/alloc/src/collections/binary_heap/mod.rs @@ -581,6 +581,40 @@ impl BinaryHeap { pub fn with_capacity_in(capacity: usize, alloc: A) -> BinaryHeap { BinaryHeap { data: Vec::with_capacity_in(capacity, alloc) } } + + /// Creates a `BinaryHeap` using the supplied `vec`. This does not rebuild the heap, + /// so `vec` must already be a max-heap. + /// + /// # Safety + /// + /// The supplied `vec` must be a max-heap, i.e. for all indices `0 < i < vec.len()`, + /// `vec[(i - 1) / 2] >= vec[i]`. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(binary_heap_from_raw_vec)] + /// + /// use std::collections::BinaryHeap; + /// let heap = BinaryHeap::from([1, 2, 3]); + /// let vec = heap.into_vec(); + /// + /// // Safety: vec is the output of heap.from_vec(), so is a max-heap. + /// let mut new_heap = unsafe { + /// BinaryHeap::from_raw_vec(vec) + /// }; + /// assert_eq!(new_heap.pop(), Some(3)); + /// assert_eq!(new_heap.pop(), Some(2)); + /// assert_eq!(new_heap.pop(), Some(1)); + /// assert_eq!(new_heap.pop(), None); + /// ``` + #[unstable(feature = "binary_heap_from_raw_vec", issue = "152500")] + #[must_use] + pub unsafe fn from_raw_vec(vec: Vec) -> BinaryHeap { + BinaryHeap { data: vec } + } } impl BinaryHeap {