Leet Code 692. Top K Frequent Words

Example 1:

Input: words = ["i","love","leetcode","i","love","coding"], k = 2
Output: ["i","love"]
Explanation: "i" and "love" are the two most frequent words.
Note that "i" comes before "love" due to a lower alphabetical order.

package pep.Day66;

import java.util.*;

public class LeetCode_692_Top_k_Frequent_Words {
    public static void main(String[] args) {
        int k = 2;
        System.out.println(topKFrequent(new String[]{"i", "love", "leetcode", "i", 

        "love", "coding"}, k));
    }

    public static List<String> topKFrequent(String[] words, int k) {
        HashMap<String, Integer> hashMap = new HashMap<>();
        for (String word : words) {
            hashMap.put(word, hashMap.getOrDefault(word, 0) + 1);
        }

        PriorityQueue<String> pq = new PriorityQueue<>(new Comparator<String>() {
            @Override
            public int compare(String child, String parent) {
                int frequency1 = hashMap.get(child);
                int frequency2 = hashMap.get(parent);

                // when count will be same then, use alphabetical order descending
                if (frequency1 == frequency2)
                    return parent.compareTo(child);
                    //return newVal - oldVal;
                return frequency1 - frequency2;
            }
        });

        for (String s : hashMap.keySet()) {
            pq.add(s);
            if (pq.size() > k)
                pq.remove();
        }

        List<String> ans = new LinkedList<>();

        while (!pq.isEmpty())
            // this will add the value to 0th index and
            // then shift previous and add next on 0th index only
            ans.add(0, pq.remove());

        return ans;
    }

}