How to arrange an array in decreasing order of frequency of each number?

Question

Input : {5, 13, 6, 5, 13, 7, 8, 6, 5}

Output : {5, 5, 5, 13, 13, 6, 6, 7, 8}

The question is to arrange the numbers in the array in

Answer 1

I can think of two solutions:

Make a first pass to count frequencies and store the first index and then sort according to that

This is simple to implement, uses linear (O(N)) additional memory in the worst case and takes O(N log N) time.

Do everything in one pass with some sort of priority queue, where the "priority" is the frequency count (changing as you pass through the input), and the index of the first occurrence to break ties

This does everything in a single pass, but I can't think of any advantage over the other solution. It still requires O(N) additional memory, and will also take O(N log N) time. Also, it requires a more complex data structure.