declaring a priority_queue in c++ with a custom comparator

Note – You may also want to check other answers, especially the one with decltype and lambda

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You should declare a class Compare and overload operator() for it like this:

class Foo
{

};

class Compare
{
public:
    bool operator() (Foo, Foo)
    {
        return true;
    }
};

int main()
{
    std::priority_queue<Foo, std::vector<Foo>, Compare> pq;
    return 0;
}

Or, if you for some reasons can’t make it as class, you could use std::function for it:

class Foo
{

};

bool Compare(Foo, Foo)
{
    return true;
}

int main()
{
    std::priority_queue<Foo, std::vector<Foo>, std::function<bool(Foo, Foo)>> pq(Compare);
    return 0;
}