STL priority_queue的自定义分配器

Question

I am trying to pass a custom allocator to STL's priority_queue . I've been able to do so for STL's vector and unordered_map , but cannot use similar syntax for priority_queue . Anyone has a hint or sample code I can use?

Note that I need to pass an instance of the allocator as one of the constructor's arguments.

Thank you

Answer 1

Unlike std::vector and std::unordered_map , which are containers, std::priority_queue is a container adaptor. It contains a container and provides special access it to. Looking at suitable reference , you can see that the second template parameter of std::priority_queue is a container ( std::vector by default). So you just need to pass your own container with a custom allocator:

std::priority_queue<T, std::vector<T, MyAllocator>> q;

Answer 2

std::priority_queue is a container adaptor. It doesn't allocate anything by itself, it defers that to the underlying container (which, by default, is std::vector with the default allocator). See also https://en.cppreference.com/w/cpp/container/priority_queue

In other words: To use a custom allocator, you have to specify a container (probably std::vector ) that uses your custom allocator as the Container template argument of std::priority_queue . Then you can use any of the std::priority_queue constructors that accepts an allocator instance.