Make min priority queue of arrays c++

Question

I want a min priority queue which instead of containing integers, stores arrays. The priority of each element is the first element in the array.

priority_queue<array<int, 6>, vector<int>, greater<int>> pq;
array<int, 6> arr = {a, b, c, d, e, f};
pq.push(arr);
array<int, 6> popArr = pq.pop();

When I do this I get the following error related to pushing:

no matching function for call to ‘std::priority_queue<std::array<int, 6>, std::vector<int>, std::greater<int> >::push(std::array<int, 6>&)’
 pq.push(arr);

And the following related to popping:

conversion from ‘void’ to non-scalar type ‘std::array<int, 6>’ requested
 array<int, 6> popArr = pq.pop();

How can I fix these errors?

Answer 1

First of all the type of data structure in priority queue is array<int,6>, so vector<int> should be written as vector<array<int,6>>.

Now the third argument is comparator. So lets create a comparator :

struct Compare{
    bool operator()(array<int,6> a,array<int,6> b){
    return a[0]>b[0];
}
};

Now declaration looks like:

priority_queue<array<int,6>, vector<array<int,6>, Compare > pq;

Also, pq.pop() return type is void, So it should be pq.top() and then write pq.pop() to remove element from priority queue .