使用`std :: greater`通过`priority_queue`创建最小堆的原因

问题描述

我想知道为什么要使用 c $>

sort_heap $ c> max_heap （最初的最大值）将反复弹出前面的 a>并根据 less （这是默认的比较运算符）

对范围进行排序，因此， c $ c> max_heap 是最大元素wrt 在前面，通过优先级队列:: top （底层 container :: front ）。

仍然可以讨论 priority_queue 与 std :: less comparator表示 max_heap 。它可以被定义为 min_heap 通过逆转比较器的参数（但是看到@TC的注释，使用C ++ 98绑定器，这是相当冗长）在呼叫到各种堆函数。一个（对我来说）反直觉的结果将是 top（）然后不会给予顶部优先级的元素

1. std::priority_queue is a container adaptor; basic memory considerations make the back the preferred place for modifications (with pop_back() and push_back()) for sequence containers such as std::vector.
2. the priority_queue primitives are based on std::make_heap (constructor), std::pop_heap + container::pop_back (priority_queue::pop) and on container::push_back + std::push_heap (priority_queue::push)
3. pop_heap will take the front of the underlying storage, and put it at the back, restoring the heap invariant afterwards. The reverse goes for push_heap.
4. doing sort_heap on a max_heap (with the max at the front initially) will repeatedly pop the front to the back and sort the range according to less (which is the default comparison operator)
5. hence, the preferred implementation of a max_heap is to have the max element w.r.t. less at the front, accessed through priority_queue::top (underlying container::front).
6. one can still debate whether it is intuitive that priority_queue with a std::less comparator is representing a max_heap. It could have been defined as a min_heap by reversing the comparator's arguments (but see the comment by @T.C. that with C++98 binders this is rather verbose) everywhere in the calls to the various heap functions. The one (for me) counter-intuitive result would have been that top() would then not have given the element with top priority

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