Description
Removes and returns the top element (the maximum under the current predicate) from the heap, then re-heapifies the remaining elements. A predicate overload is available for custom ordering.
Caveats & Gotchas
- • Calling HeapPop on an empty array triggers a bounds check crash. Always verify Num() > 0 beforehand.
- • The bool bAllowShrinking overload is deprecated in UE 5.x — use EAllowShrinking::Yes/No instead.
- • After the call the element at index 0 becomes the new maximum, but the internal order of other elements is implementation-defined and changes with each pop.
Signature
void HeapPop(ElementType& OutItem, EAllowShrinking AllowShrinking = UE::Core::Private::AllowShrinkingByDefault<AllocatorType>())Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| OutItem | ElementType& | Receives the removed top (maximum) element. | — |
| AllowShrinking | EAllowShrinking | Controls whether the array's allocation can shrink after removal. Pass EAllowShrinking::No in hot loops to avoid reallocations. | UE::Core::Private::AllowShrinkingByDefault<AllocatorType>() |
Return Type
void Example
Draining a max-heap in sorted order C++
TArray<int32> Heap = {3, 1, 4, 1, 5, 9, 2, 6};
Heap.Heapify();
while (Heap.Num() > 0)
{
int32 Top;
Heap.HeapPop(Top, EAllowShrinking::No);
UE_LOG(LogTemp, Log, TEXT("%d"), Top); // prints 9, 6, 5, 4, 3, 2, 1, 1
}Tags
Version History
Introduced in: 4.0
| Version | Status | Notes |
|---|---|---|
| 5.6 | stable | — |
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