1 class Solution {
 2 public:
 3     /*
 4      * @param nums: an integer array
 5      * @param k: An integer
 6      * @return: the top k largest numbers in array
 7      */
 8     vector<int> topk(vector<int> nums, int k) {
 9         std::priority_queue<int> heap;
10         for(int i = 0; i < nums.size(); i++) {
11             heap.push(nums[i]);
12         }
13
14         std::vector<int> result;
15         for (int i = 0; i < k; i++) {
16             result.push_back(heap.top());
17             heap.pop();
18         }
19
20         return result;
21     }
22 };

 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         int[] temp = new int[k];
 9         if(nums == null || nums.length == 0) {
10             return temp;
11         }
12         quickSort(nums, 0, nums.length - 1, k);
13
14         if(nums.length < k) {
15             return nums;
16         }
17
18         for(int i = 0; i < k; i++) {
19             temp[i] = nums[i];
20         }
21
22         return temp;
23     }
24
25     public void quickSort(int[] nums, int start, int end, int k) {
26         if (start >= end) {
27             return;
28         }
29
30         int left = start, right = end;
31         int mid = left + (right - left) / 2;
32         int pivot = nums[mid];
33
34         while(left <= right) {
35             while(left <= right && nums[left] > pivot) {
36                 left++;
37             }
38
39             while(left <= right && nums[right] < pivot) {
40                 right--;
41             }
42
43             if(left <= right) {
44                 swap(nums, left, right);
45                 left++;
46                 right--;
47             }
48         }
49
50         quickSort(nums, start, right, k);
51         quickSort(nums, left, end, k);
52     }
53
54     private void swap(int[] nums, int left, int right) {
55         int temp = nums[left];
56         nums[left] = nums[right];
57         nums[right] = temp;
58     }
59 };