template<typename _RandomAccessIterator, typename _Size, typename _Compare>
_GLIBCXX20_CONSTEXPR
void
__introselect(_RandomAccessIterator __first, _RandomAccessIterator __nth,
_RandomAccessIterator __last, _Size __depth_limit,
_Compare __comp)
{
while (__last - __first > 3)
{
if (__depth_limit == 0)
{
std::__heap_select(__first, __nth + 1, __last, __comp);
// Place the nth largest element in its final position.
std::iter_swap(__first, __nth);
return;
}
--__depth_limit;
_RandomAccessIterator __cut =
std::__unguarded_partition_pivot(__first, __last, __comp);
if (__cut <= __nth)
__first = __cut;
else
__last = __cut;
}
std::__insertion_sort(__first, __last, __comp);
}
/// This is a helper function for the sort routines.
template<typename _RandomAccessIterator, typename _Compare>
_GLIBCXX20_CONSTEXPR
void
__heap_select(_RandomAccessIterator __first,
_RandomAccessIterator __middle,
_RandomAccessIterator __last, _Compare __comp)
{
std::__make_heap(__first, __middle, __comp);
for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
if (__comp(__i, __first))
std::__pop_heap(__first, __middle, __i, __comp);
}
template<typename _RandomAccessIterator, typename _Compare>
_GLIBCXX20_CONSTEXPR
void
__make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
_Compare& __comp)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
_ValueType;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type
_DistanceType;
if (__last - __first < 2)
return;
const _DistanceType __len = __last - __first;
_DistanceType __parent = (__len - 2) / 2;
while (true)
{
_ValueType __value = _GLIBCXX_MOVE(*(__first + __parent));
std::__adjust_heap(__first, __parent, __len, _GLIBCXX_MOVE(__value),
__comp);
if (__parent == 0)
return;
__parent--;
}
}
