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#pragma once
#include <util/generic/vector.h>
#include <util/generic/algorithm.h>
#include <util/generic/maybe.h>
#include <util/str_stl.h>
template <class T, class TComparator = TGreater<T>, bool sort = true, class Alloc = std::allocator<T>>
class TTopKeeper {
private:
class TVectorWithMin {
private:
TVector<T, Alloc> Internal;
size_t HalfMaxSize;
TComparator Comparer;
size_t MinElementIndex;
private:
void Reserve() {
Internal.reserve(2 * HalfMaxSize);
}
template <class UT>
bool Insert(UT&& value) noexcept {
if (Y_UNLIKELY(0 == HalfMaxSize)) {
return false;
}
if (Internal.size() < HalfMaxSize) {
if (Internal.empty() || Comparer(Internal[MinElementIndex], value)) {
MinElementIndex = Internal.size();
Internal.push_back(std::forward<UT>(value));
return true;
}
} else if (!Comparer(value, Internal[MinElementIndex])) {
return false;
}
Internal.push_back(std::forward<UT>(value));
if (Internal.size() == (HalfMaxSize << 1)) {
Partition();
}
return true;
}
public:
using value_type = T;
TVectorWithMin(const size_t halfMaxSize, const TComparator& comp)
: HalfMaxSize(halfMaxSize)
, Comparer(comp)
{
Reserve();
}
template <class TAllocParam>
TVectorWithMin(const size_t halfMaxSize, const TComparator& comp, TAllocParam&& param)
: Internal(std::forward<TAllocParam>(param))
, HalfMaxSize(halfMaxSize)
, Comparer(comp)
{
Reserve();
}
void SortAccending() {
Sort(Internal.begin(), Internal.end(), Comparer);
}
void Partition() {
if (Y_UNLIKELY(HalfMaxSize == 0)) {
return;
}
if (Y_LIKELY(Internal.size() >= HalfMaxSize)) {
NthElement(Internal.begin(), Internal.begin() + HalfMaxSize - 1, Internal.end(), Comparer);
Internal.erase(Internal.begin() + HalfMaxSize, Internal.end());
//we should update MinElementIndex cause we just altered Internal
MinElementIndex = HalfMaxSize - 1;
}
}
bool Push(const T& value) {
return Insert(value);
}
bool Push(T&& value) {
return Insert(std::move(value));
}
template <class... TArgs>
bool Emplace(TArgs&&... args) {
return Insert(T(std::forward<TArgs>(args)...)); // TODO: make it "real" emplace, not that fake one
}
void SetMaxSize(size_t newHalfMaxSize) {
HalfMaxSize = newHalfMaxSize;
Reserve();
Partition();
}
size_t GetSize() const {
return Internal.size();
}
const auto& GetInternal() const {
return Internal;
}
auto Extract() {
using std::swap;
decltype(Internal) values;
swap(Internal, values);
Reset();
return values;
}
const T& Back() const {
return Internal.back();
}
void Pop() {
Internal.pop_back();
}
void Reset() {
Internal.clear();
//MinElementIndex will reset itself when we start adding new values
}
};
void CheckNotFinalized() {
Y_ENSURE(!Finalized, "Cannot insert after finalizing (Pop() / GetNext() / Finalize())! "
"Use TLimitedHeap for this scenario");
}
size_t MaxSize;
const TComparator Comparer;
TVectorWithMin Internal;
bool Finalized;
public:
TTopKeeper()
: MaxSize(0)
, Comparer()
, Internal(0, Comparer)
, Finalized(false)
{
}
TTopKeeper(size_t maxSize, const TComparator& comp = TComparator())
: MaxSize(maxSize)
, Comparer(comp)
, Internal(maxSize, comp)
, Finalized(false)
{
}
template <class TAllocParam>
TTopKeeper(size_t maxSize, const TComparator& comp, TAllocParam&& param)
: MaxSize(maxSize)
, Comparer(comp)
, Internal(maxSize, comp, std::forward<TAllocParam>(param))
, Finalized(false)
{
}
void Finalize() {
if (Y_LIKELY(Finalized)) {
return;
}
Internal.Partition();
if (sort) {
Internal.SortAccending();
}
Finalized = true;
}
const T& GetNext() {
Y_ENSURE(!IsEmpty(), "Trying GetNext from empty heap!");
Finalize();
return Internal.Back();
}
void Pop() {
Y_ENSURE(!IsEmpty(), "Trying Pop from empty heap!");
Finalize();
Internal.Pop();
if (IsEmpty()) {
Reset();
}
}
T ExtractOne() {
Y_ENSURE(!IsEmpty(), "Trying ExtractOne from empty heap!");
Finalize();
auto value = std::move(Internal.Back());
Internal.Pop();
if (IsEmpty()) {
Reset();
}
return value;
}
auto Extract() {
Finalize();
return Internal.Extract();
}
bool Insert(const T& value) {
CheckNotFinalized();
return Internal.Push(value);
}
bool Insert(T&& value) {
CheckNotFinalized();
return Internal.Push(std::move(value));
}
template <class... TArgs>
bool Emplace(TArgs&&... args) {
CheckNotFinalized();
return Internal.Emplace(std::forward<TArgs>(args)...);
}
const auto& GetInternal() {
Finalize();
return Internal.GetInternal();
}
bool IsEmpty() const {
return Internal.GetSize() == 0;
}
size_t GetSize() const {
return Min(Internal.GetSize(), MaxSize);
}
size_t GetMaxSize() const {
return MaxSize;
}
void SetMaxSize(size_t newMaxSize) {
Y_ENSURE(!Finalized, "Cannot resize after finalizing (Pop() / GetNext() / Finalize())! "
"Use TLimitedHeap for this scenario");
MaxSize = newMaxSize;
Internal.SetMaxSize(newMaxSize);
}
void Reset() {
Internal.Reset();
Finalized = false;
}
};
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