LC_347

class Solution {
    public int[] topKFrequent(int[] nums, int k) {
        HashMap<Integer, Integer> map = new HashMap<>();
        for(int num : nums){
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        PriorityQueue<int[]> maxHeap = new PriorityQueue<>(
            (a,b) -> b[1] - a[1]
        );
        for(Map.Entry<Integer,Integer> entry : map.entrySet()){
            maxHeap.offer(new int[]{
                entry.getKey(),
                entry.getValue()
            });
        }
        int[] ans = new int[k];
        for(int i = 0; i < k; i++){
            ans[i] = maxHeap.poll()[0];
        }
        return ans;
    }
}