How do I implement a comparator for a priority queue in C++11?

How do I implement a comparator for a priority queue in C++11?

You can implement a comparator by defining a struct or a lambda function that specifies the ordering of elements.

Can you show me an example using a struct?

Sure! Here's a simple example:

struct Compare {
    bool operator()(const int& a, const int& b) {
        return a > b; // Min-heap
    }
};

std::priority_queue<int, std::vector<int>, Compare> pq;

What if I want a max-heap instead?

For a max-heap, you can simply change the comparison in the struct to return a < b;. This will ensure the largest element is at the top.

Can I use a lambda function instead of a struct?

Absolutely! You can define the priority queue like this:

auto cmp = [](int left, int right) { return left > right; };
std::priority_queue<int, std::vector<int>, decltype(cmp)> pq(cmp);