Untitled

import java.util.*;

public class TopKFrequentElements {
    public int[] topKFrequent(int[] nums, int k) {
        // Step 1: Build a frequency map
        Map<Integer, Integer> frequencyMap = new HashMap<>();
        for (int num : nums) {
            frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1);
        }

        // Step 2: Use a min-heap to keep track of top k frequent elements
        PriorityQueue<int[]> minHeap = new PriorityQueue<>((a, b) -> a[1] - b[1]); // Compare by frequency
        for (Map.Entry<Integer, Integer> entry : frequencyMap.entrySet()) {
            minHeap.offer(new int[]{entry.getKey(), entry.getValue()});
            if (minHeap.size() > k) {
                minHeap.poll(); // Remove the least frequent element
            }
        }

        // Step 3: Extract elements from the heap
        int[] result = new int[k];
        int index = 0;
        while (!minHeap.isEmpty()) {
            result[index++] = minHeap.poll()[0];
        }
        return result;
    }

    public static void main(String[] args) {
        TopKFrequentElements solution = new TopKFrequentElements();

        // Example 1
        int[] nums1 = {1, 1, 1, 2, 2, 3};
        int k1 = 2;
        System.out.println(Arrays.toString(solution.topKFrequent(nums1, k1))); // Output: [1, 2]

        // Example 2
        int[] nums2 = {1};
        int k2 = 1;
        System.out.println(Arrays.toString(solution.topKFrequent(nums2, k2))); // Output: [1]
    }
}