C++ C++;优先级队列不符合FIFO顺序
我正在使用STL优先级队列收集我自己的类Lettura的对象C++ C++;优先级队列不符合FIFO顺序,c++,priority-queue,fifo,C++,Priority Queue,Fifo,我正在使用STL优先级队列收集我自己的类Lettura的对象 //---------LETTURA---------- enum Priority {zero, standard, urgent}; class Lettura{ public: int valore; char sensore; Priority priorita; Lettura(): valore(0),sensore('\0'),priorita(zero){} Lettura(const int val, con
//---------LETTURA----------
enum Priority {zero, standard, urgent};
class Lettura{
public:
int valore;
char sensore;
Priority priorita;
Lettura(): valore(0),sensore('\0'),priorita(zero){}
Lettura(const int val, const char s='\0', const Priority p=zero): valore(val),sensore(s), priorita(p){}
friend ostream& operator<<(ostream& out, const Lettura & lett);
};
我希望以FIFO顺序使用相同的优先级元素:
top: l5 urgent
top: l1 standard
top: l2 standard
top: l3 standard
top: l4 standard
top: l6 standard
这是我的代码:
int main() {
std::priority_queue<Lettura, std::vector<Lettura>, std::less<Lettura> > coda;
Lettura l1(50,'a',standard);
Lettura l2(50,'b',standard);
Lettura l3(120,'c',standard);
Lettura l4(100,'d',standard);
Lettura l5(30,'e',urgent);
Lettura l6(35,'f',standard);
coda.push(l1);
coda.push(l2);
coda.push(l3);
coda.push(l4);
coda.push(l5);
coda.push(l6);
cout<<"top: "<<coda.top()<<"\n"; coda.pop();
cout<<"top: "<<coda.top()<<"\n"; coda.pop();
cout<<"top: "<<coda.top()<<"\n"; coda.pop();
cout<<"top: "<<coda.top()<<"\n"; coda.pop();
cout<<"top: "<<coda.top()<<"\n"; coda.pop();
cout<<"top: "<<coda.top()<<"\n"; coda.pop();
}
intmain(){
std::优先级队列尾码;
Lettura l1(50,'a',标准);
Lettura l2(50,'b',标准);
Lettura l3(120,'c',标准);
Lettura l4(100,'d',标准);
Lettura l5(30,'e',紧急);
Lettura l6(35,'f',标准);
尾波推力(l1);
尾波推力(l2);
尾波推力(l3);
尾波推力(l4);
尾波推力(l5);
尾波推力(l6);
cout您的代码似乎正常工作,因为您首先获取紧急项目。在基于堆的优先级队列中,没有按插入时间进行子排序,因此您将以未定义的顺序获取具有相同优先级的项目,只是它们将位于具有更高优先级的项目之后。您需要添加一个额外字段,例如“时间投入”队列,并将其与优先级枚举一起使用在比较运算符中。 它似乎是编译器库和C++标准的一个bug。它们打破了PrimRythyQueLe中最大元素的选择算法。
我将准备相应的方案。这里是一个稳定优先级队列的简单实现
每当队列为空时,它会尝试通过将插入计数器归零来阻止排序耗尽:
#include <iostream>
#include <string>
#include <queue>
#include <algorithm>
enum Priority
{
zero, standard, urgent
};
inline std::ostream& operator <<(std::ostream& os, const Priority& p)
{
switch (p) {
case zero:
return os << "zero";
case standard:
return os << "standard";
case urgent:
return os << "urgent";
}
}
class Lettura
{
public:
int valore;
char sensore;
Priority priorita;
Lettura()
: valore(0)
, sensore('\0')
, priorita(zero) {}
Lettura(const int val, const char s = '\0', const Priority p = zero)
: valore(val)
, sensore(s)
, priorita(p) {}
friend std::ostream& operator <<(std::ostream& out, const Lettura& lett)
{
return out << "{ valore: " << lett.valore << ", sensore: " << lett.sensore << ", priorita: " << lett.priorita
<< " }";
}
};
template<class T, class Comp>
struct stable_priority_queue
{
using counter_type = std::size_t;
struct Proxy
{
Proxy(T&& o, counter_type c)
: object(std::move(o))
, insertion_order_(c) {}
Proxy(const T& o, counter_type c)
: object(o)
, insertion_order_(c) {}
T object;
counter_type insertion_order_;
};
struct ProxyComp
{
bool operator ()(Proxy const& l, Proxy const& r) const
{
if (major_order_(l.object, r.object))
return true;
if (major_order_(r.object, l.object))
return false;
return minor_order_(l.insertion_order_, r.insertion_order_);
}
Comp major_order_;
std::greater<> minor_order_;
};
decltype(auto) push(T item)
{
return queue_.emplace(std::move(item), counter_++);
}
T const& top() const
{
return queue_.top().object;
}
void pop()
{
queue_.pop();
if (queue_.empty())
counter_ = 0;
}
std::priority_queue<Proxy, std::vector<Proxy>, ProxyComp> queue_;
counter_type counter_ = 0;
};
struct lower_priority
{
bool operator ()(const Lettura& l, const Lettura& r) const
{
return l.priorita < r.priorita;
}
};
int main()
{
stable_priority_queue<Lettura, lower_priority> coda;
Lettura l1(50, 'a', standard);
Lettura l2(50, 'b', standard);
Lettura l3(120, 'c', standard);
Lettura l4(100, 'd', standard);
Lettura l5(30, 'e', urgent);
Lettura l6(35, 'f', standard);
coda.push(l1);
coda.push(l2);
coda.push(l3);
coda.push(l4);
coda.push(l5);
coda.push(l6);
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
}
下面是另一种可能的稳定的优先级队列实现,它保持优先级队列提供的相同接口:
template <class T>
struct stable_element
{
stable_element(T&& o, std::size_t c)
: object_(std::move(o))
, insertion_order_(c)
{
}
stable_element(const T& o, std::size_t c)
: object_(o)
, insertion_order_(c)
{
}
operator T() { return object_; }
T object_;
std::size_t insertion_order_;
};
template <class T>
bool operator<(const stable_element<T>& lhs, const stable_element<T>& rhs)
{
return (lhs.object_ < rhs.object_) || (!(rhs.object_ < lhs.object_) && (rhs.insertion_order_ < lhs.insertion_order_));
}
template <class T,
class Container = std::vector<stable_element<T>>,
class Compare = std::less<typename Container::value_type>>
class stable_priority_queue : public std::priority_queue<stable_element<T>, Container, Compare>
{
using stableT = stable_element<T>;
using std::priority_queue<stableT, Container, Compare>::priority_queue;
public:
const T& top() { return this->c.front().object_; }
void push(const T& value) {
this->c.push_back(stableT(value, counter_++));
std::push_heap(this->c.begin(), this->c.end(), this->comp);
}
void push(T&& value) {
this->c.push_back(stableT(std::move(value), counter_++));
std::push_heap(this->c.begin(), this->c.end(), this->comp);
}
template<class ... Args>
void emplace(Args&&... args) {
this->c.emplace_back(T(std::forward<Args>(args)...), counter_++);
std::push_heap(this->c.begin(), this->c.end(), this->comp);
}
void pop() {
std::pop_heap(this->c.begin(), this->c.end(), this->comp);
this->c.pop_back();
if (this->empty()) counter_ = 0;
}
protected:
std::size_t counter_ = 0;
};
输出:
top: { valore: 30, sensore: e, priorita: urgent }
top: { valore: 50, sensore: a, priorita: standard }
top: { valore: 50, sensore: b, priorita: standard }
top: { valore: 120, sensore: c, priorita: standard }
top: { valore: 100, sensore: d, priorita: standard }
top: { valore: 35, sensore: f, priorita: standard }
这里是所有这些组合的一个演示您显示的是值11、12、13、14、15,但推送的是值50、50、100等等。您使用的是什么值?这些值不是11、12…而是l1、l2、l3…带有“L”而不是“1”。从该链接看不出它是编译器错误还是标准错误-这只是您对它应该如何运行的看法rk,我不想在这里讨论。在这两种情况下,它对OP都没有帮助。@latedeveloper这意味着只有一件事你不知道有堆的算法。很多关于算法的书中都描述了它们。请在阅读之前阅读它们,对书中的算法说些什么,书中描述了如何选择元素。你能补充一下吗有什么解释吗?@ConfusedByCode我扩展了我的答案。希望这现在更清楚了
#include <iostream>
#include <string>
#include <queue>
#include <algorithm>
enum Priority
{
zero, standard, urgent
};
inline std::ostream& operator <<(std::ostream& os, const Priority& p)
{
switch (p) {
case zero:
return os << "zero";
case standard:
return os << "standard";
case urgent:
return os << "urgent";
}
}
class Lettura
{
public:
int valore;
char sensore;
Priority priorita;
Lettura()
: valore(0)
, sensore('\0')
, priorita(zero) {}
Lettura(const int val, const char s = '\0', const Priority p = zero)
: valore(val)
, sensore(s)
, priorita(p) {}
friend std::ostream& operator <<(std::ostream& out, const Lettura& lett)
{
return out << "{ valore: " << lett.valore << ", sensore: " << lett.sensore << ", priorita: " << lett.priorita
<< " }";
}
};
template<class T, class Comp>
struct stable_priority_queue
{
using counter_type = std::size_t;
struct Proxy
{
Proxy(T&& o, counter_type c)
: object(std::move(o))
, insertion_order_(c) {}
Proxy(const T& o, counter_type c)
: object(o)
, insertion_order_(c) {}
T object;
counter_type insertion_order_;
};
struct ProxyComp
{
bool operator ()(Proxy const& l, Proxy const& r) const
{
if (major_order_(l.object, r.object))
return true;
if (major_order_(r.object, l.object))
return false;
return minor_order_(l.insertion_order_, r.insertion_order_);
}
Comp major_order_;
std::greater<> minor_order_;
};
decltype(auto) push(T item)
{
return queue_.emplace(std::move(item), counter_++);
}
T const& top() const
{
return queue_.top().object;
}
void pop()
{
queue_.pop();
if (queue_.empty())
counter_ = 0;
}
std::priority_queue<Proxy, std::vector<Proxy>, ProxyComp> queue_;
counter_type counter_ = 0;
};
struct lower_priority
{
bool operator ()(const Lettura& l, const Lettura& r) const
{
return l.priorita < r.priorita;
}
};
int main()
{
stable_priority_queue<Lettura, lower_priority> coda;
Lettura l1(50, 'a', standard);
Lettura l2(50, 'b', standard);
Lettura l3(120, 'c', standard);
Lettura l4(100, 'd', standard);
Lettura l5(30, 'e', urgent);
Lettura l6(35, 'f', standard);
coda.push(l1);
coda.push(l2);
coda.push(l3);
coda.push(l4);
coda.push(l5);
coda.push(l6);
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
std::cout << "top: " << coda.top() << "\n";
coda.pop();
}
top: { valore: 30, sensore: e, priorita: urgent }
top: { valore: 50, sensore: a, priorita: standard }
top: { valore: 50, sensore: b, priorita: standard }
top: { valore: 120, sensore: c, priorita: standard }
top: { valore: 100, sensore: d, priorita: standard }
top: { valore: 35, sensore: f, priorita: standard }
template <class T>
struct stable_element
{
stable_element(T&& o, std::size_t c)
: object_(std::move(o))
, insertion_order_(c)
{
}
stable_element(const T& o, std::size_t c)
: object_(o)
, insertion_order_(c)
{
}
operator T() { return object_; }
T object_;
std::size_t insertion_order_;
};
template <class T>
bool operator<(const stable_element<T>& lhs, const stable_element<T>& rhs)
{
return (lhs.object_ < rhs.object_) || (!(rhs.object_ < lhs.object_) && (rhs.insertion_order_ < lhs.insertion_order_));
}
template <class T,
class Container = std::vector<stable_element<T>>,
class Compare = std::less<typename Container::value_type>>
class stable_priority_queue : public std::priority_queue<stable_element<T>, Container, Compare>
{
using stableT = stable_element<T>;
using std::priority_queue<stableT, Container, Compare>::priority_queue;
public:
const T& top() { return this->c.front().object_; }
void push(const T& value) {
this->c.push_back(stableT(value, counter_++));
std::push_heap(this->c.begin(), this->c.end(), this->comp);
}
void push(T&& value) {
this->c.push_back(stableT(std::move(value), counter_++));
std::push_heap(this->c.begin(), this->c.end(), this->comp);
}
template<class ... Args>
void emplace(Args&&... args) {
this->c.emplace_back(T(std::forward<Args>(args)...), counter_++);
std::push_heap(this->c.begin(), this->c.end(), this->comp);
}
void pop() {
std::pop_heap(this->c.begin(), this->c.end(), this->comp);
this->c.pop_back();
if (this->empty()) counter_ = 0;
}
protected:
std::size_t counter_ = 0;
};
enum Priority
{
zero, standard, urgent
};
inline std::ostream& operator <<(std::ostream& os, const Priority& p)
{
switch (p) {
case zero:
os << "zero"; break;
case standard:
os << "standard"; break;
case urgent:
os << "urgent"; break;
}
return os;
}
class Lettura
{
public:
int valore;
char sensore;
Priority priorita;
Lettura()
: valore(0)
, sensore('\0')
, priorita(zero) {}
Lettura(const int val, const char s = '\0', const Priority p = zero)
: valore(val)
, sensore(s)
, priorita(p) {}
friend std::ostream& operator <<(std::ostream& out, const Lettura& lett)
{
return out << "{ valore: " << lett.valore << ", sensore: " << lett.sensore << ", priorita: " << lett.priorita
<< " }";
}
};
bool operator<(const Lettura& l, const Lettura& r)
{
return l.priorita < r.priorita;
}
int main()
{
stable_priority_queue<Lettura> coda;
Lettura l1(50, 'a', standard);
Lettura l2(50, 'b', standard);
Lettura l3(120, 'c', standard);
Lettura l5(30, 'e', urgent);
Lettura l6(35, 'f', standard);
coda.push(l1);
coda.push(l2);
coda.push(l3);
coda.emplace(100, 'd', standard);
coda.emplace(l5);
coda.emplace(l6);
while (!coda.empty()) {
std::cout << "top: " << coda.top() << "\n";
coda.pop();
}
}
top: { valore: 30, sensore: e, priorita: urgent }
top: { valore: 50, sensore: a, priorita: standard }
top: { valore: 50, sensore: b, priorita: standard }
top: { valore: 120, sensore: c, priorita: standard }
top: { valore: 100, sensore: d, priorita: standard }
top: { valore: 35, sensore: f, priorita: standard }