C++ 优先队列清除方法
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priority queue clear method
提问by russell
How do I delete all elements from a priority queue? That means how do I destroy a priority queue? advanced thanks for your answer. Is there any clear- or erase-like method?
如何从优先级队列中删除所有元素？这意味着我如何销毁优先队列？高级感谢您的回答。有没有类似清除或擦除的方法？
回答by
The priority_queue interface doesn't have a clear() method (for no good reason I've ever been able to discern). A simple way to clear it is just to assign a new, empty queue:
priority_queue 接口没有 clear() 方法（没有充分的理由我一直能够辨别）。清除它的一种简单方法是分配一个新的空队列：
priority_queue <int> q;
// use it
q = priority_queue <int>(); // reset it
回答by Richard
priority_queuedoesn't have a clear method. It may be that this is for interface simplicity, or because it there may be situations in which elements must be destroyed in priority-order, making a generic clear function unsafe.
priority_queue没有明确的方法。这可能是为了接口简单，或者因为可能存在必须按优先级顺序销毁元素的情况，从而使通用的 clear 函数变得不安全。
Regardless, the following code block includes two functions to clear priority queues. The first works by building a temporary instance of a wrapper class around the priority_queue and then using this to access the underlying storage object, which is assumed to have a clear()method. The second works by replacing the existing priority_queue with a new queue.
无论如何，以下代码块包括两个清除优先级队列的函数。第一种方法是围绕priority_queue 构建一个包装类的临时实例，然后使用它来访问底层存储对象，假设它有一个clear()方法。第二个通过用新队列替换现有的 priority_queue 来工作。
I use templating so that the functions can be recycled time and again.
我使用模板，以便可以一次又一次地回收这些功能。
#include <queue>
#include <iostream>
using namespace std;
template <class T, class S, class C>
void clearpq(priority_queue<T, S, C>& q) {
struct HackedQueue : private priority_queue<T, S, C> {
static S& Container(priority_queue<T, S, C>& q) {
return q.*&HackedQueue::c;
}
};
HackedQueue::Container(q).clear();
}
template <class T, class S, class C>
void clearpq2(priority_queue<T, S, C>& q){
q=priority_queue<T, S, C>();
}
int main(){
priority_queue<int> testq, testq2;
//Load priority queue
for(int i=0;i<10;++i)
testq.push(i);
testq2=testq;
//Establish it is working
cout<<testq.top()<<endl;
testq.pop();
cout<<testq.top()<<endl;
testq.pop();
//Clear it and prove that it worked
clearpq(testq);
cout<<testq.size()<<endl;
//Use the second clearing function
cout<<testq2.size()<<endl;
clearpq2(testq2);
cout<<testq2.size()<<endl;
}
回答by Jonathan Lidbeck
Here's a clean and simple method to clear any priority_queue(and queue, and most other containers as well):
这是清除任何priority_queue（和queue，以及大多数其他容器）的干净简单的方法：
template <class Q>
void clearQueue(Q & q) {
q = Q();
}
Since it's a template, you don't have to remember all the template parameters.
由于它是一个模板，因此您不必记住所有模板参数。
Example:
例子：
std::priority_queue<MyType> simpleQueue;
std::priority_queue<MyType, std::deque<MyType>, MyHashFunction> customQueue;
// ... later ...
clearQueue(customQueue);
clearQueue(simpleQueue);
回答by Manjunath Bhadrannavar
there is no clear method supported for priority_queue in c++ but, this below is a good method to clear the priority_queue and has O(log(n)) time
在 C++ 中没有支持 priority_queue 的 clear 方法，但是，下面是清除 priority_queue 的好方法，并且有 O(log(n)) 时间
while (!pq.empty())
pq.pop();
回答by íhor Mé
priority_queue<int> a;
a.push(10);
a.push(9);
a.push(8);
a = {};
a.push(1);
a.push(4);
a.push(6);
while(!a.empty())
{
std::cout<< a.top();
a.pop();
}
results in
结果是
641
So you can simply
所以你可以简单地
a = {};
回答by bhilburn
As any C++ STL reference will show you, the STL Priority Queue class does not have a function like 'clear' or 'erase'. http://www.cplusplus.com/reference/stl/priority_queue/
正如任何 C++ STL 参考将向您展示的那样，STL Priority Queue 类没有像“clear”或“erase”这样的函数。 http://www.cplusplus.com/reference/stl/priority_queue/
It is a container class, and as such, a very simple destructor is generated by the compiler (in most cases). If your priority queue uses only locally-allocated information in its nodes, then this should work fine for clearing out the memory.
它是一个容器类，因此，编译器会生成一个非常简单的析构函数（在大多数情况下）。如果您的优先级队列仅在其节点中使用本地分配的信息，那么这应该可以很好地清除内存。
However, if you have dynamically allocated memory for the information in your priority queue, you will need to manually create a 'clear'-like function.
但是，如果您已为优先级队列中的信息动态分配内存，则需要手动创建类似“清除”的函数。
Hope this helps!
希望这可以帮助！
