Mirror/TrinityCore
1
0
Fork 0
mirror of https://github.com/TrinityCore/TrinityCore.git synced 2026-01-19 08:55:32 +01:00
Code Issues Packages Projects Releases Wiki Activity

Utilities/Containers: New RandomResize implementation with guaranteed asymptotic linear time for all container types (#19974)

Browse Source
This commit is contained in:
Treeston
2017-07-06 19:51:16 +02:00
committed by GitHub
parent 2dd658cacc
commit ac50034df7
1 changed files with 18 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/common/Utilities/Containers.h
View File

@@ -53,17 +53,29 @@ namespace Trinity
return size;
}
// resizes <container> to have at most <requestedSize> elements
// if it has more than <requestedSize> elements, the elements to keep are selected randomly
template<class C>
void RandomResize(C& container, std::size_t requestedSize)
{
uint32 currentSize = uint32(Size(container));
while (currentSize > requestedSize)
static_assert(std::is_base_of<std::forward_iterator_tag, typename std::iterator_traits<typename C::iterator>::iterator_category>::value, "Invalid container passed to Trinity::Containers::RandomResize");
if (Size(container) <= requestedSize)
return;
auto keepIt = std::begin(container), curIt = std::begin(container);
uint32 elementsToKeep = requestedSize, elementsToProcess = Size(container);
while (elementsToProcess)
{
auto itr = std::begin(container);
std::advance(itr, urand(0, currentSize - 1));
container.erase(itr);
--currentSize;
// this element has chance (elementsToKeep / elementsToProcess) of being kept
if (urand(1, elementsToProcess) <= elementsToKeep)
{
*keepIt = std::move(*curIt);
++keepIt;
--elementsToKeep;
}
++curIt;
--elementsToProcess;
}
container.erase(keepIt, std::end(container));
}
template<class C, class Predicate>