Leetcode 347

class Solution {
    public int[] topKFrequent(int[] nums, int k) {
        // don't think quicksort is acutally good here 
        int[] res = new int[k];
        HashMap<Integer,Integer> count = new HashMap<>();
        for(int n : nums){
            if(count.containsKey(n)){
                count.put(n,count.get(n) + 1);
            }else{
                count.put(n,1);
            }
        }
        PriorityQueue<int[]> pq = new PriorityQueue<>((a,b) -> {return b[1] - a[1];});
        for(int key : count.keySet()){
            pq.add(new int[]{key,count.get(key)});
        }
        for(int i = 0; i < k; i ++){
            res[i] = pq.poll()[0];
        }
        return res;
    }
}