![]() ![]() Yes, I know this is silly stuff, but I guess that it shows that the priority_queue adaptor prevents you from doing things that you expect to be able to do with vector, like shrinking the capacity. To implement a priority queue in C++, follow these steps: 1. (implicitly declared) 2) Move assignment operator. Replaces the contents with a copy of the contents of other. Replaces the contents of the container adaptor with those of other. In C++, you can use the priorityqueue container from the Standard Library, which by default operates as a max-heap. std::priorityqueue:: operator.Std::cout << "Capacity is " << capacity(q) << '\n' A priority queue is a data structure that stores elements while maintaining their order with respect to their priority. Std::vector& v_tmp = *reinterpret_cast*>(& tmp) Std::vector& v = *reinterpret_cast*>(& q) (2) If you assume that it is a vector implementation and that the vector implementation is at the beginning of the priority_queue class (yes, an evil assumption), you see swap working on VC7.1, getting the capacity to shrink with priority_queues but not on GNU 3.2, unless you cast the containers as vectors, when you swap.Ä«ool operator int capacity(std::priority_que ue& q) The priority_queue adaptor restricts you in what you can do with the vector implementation (assuming it is indeed a vector implementation). It is similar to the ordinary queue in certain aspects but differs in. The queue follows the FIFO policy while priority queue pops the elements based on the priority, i.e., the highest priority element is popped first. You use the container adapter priorityqueue to manage an underlying container as a priority queue. The priority queue in C++ is a derived container in STL that considers only the highest priority element. (1) The syntax I suggested previously was wrong and it couldn't have been used anyhow because there is no swap function in priority_queue. The template class describes an object that controls a varying-length ordered sequence of elements that has limited access. I've had a little play with the copy and swap with this and I found out a few things. In the first example, the pq object goes out of scope when the program terminates It happens in the second example because the pq object goes out of scope before the program terminates. Someclass(int a1, int b1, int c1, int d1, int e1) to goevrn when pq goes out of scope ![]()
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