Lc0347Solution.java

package top;

import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;

public class Lc0347Solution {
    
    public int[] topKFrequent(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        PriorityQueue<int[]> queue = new PriorityQueue<>((m, n) -> {
            return m[1] - n[1];
        });
        for (int i : nums) {
            map.put(i, map.getOrDefault(i, 0) + 1);
        }
        for (Map.Entry<Integer, Integer> e : map.entrySet()) {
            int num = e.getKey(), count = e.getValue();
            if (queue.size() == k) {
                if (queue.peek()[1] < count) {
                    queue.poll();
                    queue.offer(new int[] {num, count});
                }
            } else {
                queue.offer(new int[] {num, count});
            }
        }
        int[] ret = new int[k];
        for (int i = 0; i < k; i++) {
            ret[i] = queue.poll()[0];
        }
        return ret;
    }
}