347. Top K Frequent Elements

leetcode.com/problems/top-k-frequent-elements/

class Solution {
    
    /**
    1. priority queue
    2. array and sort
    
    */
    public int[] topKFrequent(int[] nums, int k) {
        
        // {num : cnt}
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        for(int num : nums) {
            if(map.containsKey(num)) {
                map.put(num, map.get(num) + 1);
            } else {
                map.put(num, 1);
            }
        }
        
        PriorityQueue<Data> pq = new PriorityQueue<>(k, (a, b) -> b.cnt - a.cnt);
        
        for(Map.Entry<Integer, Integer> e : map.entrySet()) {
            pq.offer(new Data(e.getKey(), e.getValue()));
        }
        
        int[] ans = new int[k];
        for(int i=0; i<k; i++) {
            ans[i] = pq.poll().val;
        }
        return ans;
    }
    
    class Data {
        public int val;
        public int cnt;
        public Data(int val, int cnt) {
            this.val = val;
            this.cnt = cnt;
        }
    }
    
        
}

leetcode.com/problems/top-k-frequent-elements/discuss/81635/3-Java-Solution-using-Array-MaxHeap-TreeMap

3 Java Solution using Array, MaxHeap, TreeMap - LeetCode Discuss