Top k Largest Numbers

 1 class Solution {
 2     /*
 3      * @param nums an integer array
 4      * @param k an integer
 5      * @return the top k largest numbers in array
 6      */
 7     public int[] topk(int[] nums, int k) {
 8         if (nums == null || nums.length < k) {
 9             return null;
10         }
11         
12         int[] result = new int[k];
13         PriorityQueue<Integer> minHeap = new PriorityQueue<>();
14         for (int i = 0; i < nums.length; i++) {
15             if (minHeap.size() < k) {
16                 minHeap.add(nums[i]);
17             } else {
18                 int temp = minHeap.poll();
19                 minHeap.add(Math.max(temp, nums[i]));
20             }
21         }
22         
23         for (int i = k - 1; i >= 0; i--) {
24             result[i] = minHeap.poll();
25         }
26         
27         return result;
28     }
29 };