Why does std::priority_queue use max heap instead of min heap?

Question

I always wondered why STL priority queue uses max heap instead of min heap by default. Two obvious use cases that come to mind is pathfinding (Dijkstra) and building Huffman codes. Both algorithms need to pull min elements first. Since sorting (std::sort) uses ascending order by default, I wonder what was the design reasoning behind priority_queue, because I would very much prefer a min heap by default.

Answer 1

Priority_queue is adapted from make_heap/pop_heap/push_heap/sort_heap. When you make_heap with less, the elements are sorted ascending. And the last element is treated as root element. So it is max heap. I guess there are two reasons:

1. We always use less in all default STL sorting.
2. push_back() or pop_back() is much more efficient than push_front() or pop_front().