priority_queue with custom comparator returning wrong top-of-the-heap

Question

I'm wondering why does the following code return the element with 10 as top element

class mycomparison
{
public:
  bool operator() (pair<int, Node*> e1, pair<int, Node*> e2) const {
    return e1.first < e2.first;
  };
};

  priority_queue<pair<int, Node*>, vector<pair<int, Node*>>, mycomparison> queue;
  queue.push(make_pair(4, &root));
  queue.push(make_pair(10, &root));
  auto var = queue.top();

Shouldn't it return the 4 element?

Answer 1

The C++ priority queue is a max -heap; the largest element is on top .