优先队列比较 [英] Priority Queue Comparison

问题描述

我正在尝试使用自定义比较函数在c ++中声明优先级队列...

I'm trying to declare a priority queue in c++ using a custom comparison function...

因此，我将队列声明如下:

So , I declare the queue as follows:

std::priority_queue<int,std::vector<int>, compare> pq;

这是比较功能:

bool compare(int a, int b)
{
   return (a<b);
}

我很确定我以前以类似的方式在没有类的情况下进行了此操作，但是现在，此代码无法编译，并且出现了类似以下的错误:

I'm pretty sure I did this before, without a class,in a similar way, but now, this code doesn't compile and I get several errors like this :

type/value mismatch at argument 3 in template parameter list for 'template<class _Tp, class _Sequence, class _Compare> class std::priority_queue'

是否可以创建与此类似但不使用类的比较函数?

Is there a way to create a compare function similar to this but without using a class?

谢谢

推荐答案

模板参数应为比较功能的类型.然后，该函数可以是默认构造的，也可以在 priority_queue 的构造函数中传递一个函数.所以尝试

The template parameter should be the type of the comparison function. The function is then either default-constructed or you pass a function in the constructor of priority_queue. So try either

std::priority_queue<int, std::vector<int>, decltype(&compare)> pq(&compare);

或不使用函数指针，而是使用标准库中的函子，然后可以对其进行默认构造，从而无需在构造函数中传递实例:

or don't use function pointers but instead a functor from the standard library which then can be default-constructed, eliminating the need of passing an instance in the constructor:

std::priority_queue<int, std::vector<int>, std::less<int> > pq;

http://ideone.com/KDOkJf

如果无法使用标准库函子来表达您的比较函数(以防您在优先级队列中使用自定义类)，建议您编写一个自定义函子类，

If your comparison function can't be expressed using standard library functors (in case you use custom classes in the priority queue), I recommend writing a custom functor class, or use a lambda.

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