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I know the std::priority_queue class implements a minheap. Is there a way to use this as a Max heap? Or is there an alternative Maxheap structure? I know I can use the std::make_heap() function on a std::vector with lambda to create my own Maxheap but then using functions such as std::pop_heap() is weird and I don't think they are easy to use. There should be an easier way just like the min_heap(priority queue) I think.
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Memory in a C/C++/Java program can either be allocated on a stack or a heap.
A Binary Heap is a complete binary tree which is either Min Heap or Max Heap. In a Max Binary Heap, the key at root must be maximum among all keys present in Binary Heap. This property must be recursively true for all nodes in Binary Tree.
make_heap() in C++ STL. make_heap() is used to transform a sequence into a heap. A heap is a data structure which points to highest( or lowest) element and making its access in O(1) time. Order of all the other elements depends upon particular implementation, but remains consistent throughout.
Regarding std::priority_queue:
A user-provided
Comparecan be supplied to change the ordering, e.g. usingstd::greater<T>would cause the smallest element to appear as thetop().
Since std::less<T> is the default template argument to the Compare template parameter, it is already a max heap by default. If you want a min heap instead (what the quote above suggest), pass std::greater<T> instead of std::less<T> as the template argument.
To summarize:
std::less<T> (this is the default template argument).std::greater<T>.Note that std::priority_queue is actually a container adapter (in contrast to a data structure). It doesn't specify what underlying data structure is using. However, due to the specified run-time complexity of the operations push(), pop() and top(), it is likely implemented as a heap.
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