215. Kth Largest Element in an Array java solutions

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example,
Given [3,2,1,5,6,4] and k = 2, return 5.

Note:
You may assume k is always valid, 1 ≤ k ≤ array's length.

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

1 public class Solution {
2     public int findKthLargest(int[] nums, int k) {
3         Arrays.sort(nums);
4         return nums[nums.length-k];
5     }
6 }

解法二：

维护一个大小为k 的最小堆，遍历一遍数组，再返回最小堆的顶部元素即为第k大元素。

 1 public class Solution {
 2     public int findKthLargest(int[] nums, int k) {
 3         PriorityQueue<Integer> q = new PriorityQueue<Integer>(k+1);
 4         for(int n : nums){
 5             q.offer(n);
 6             if(q.size() > k) q.poll();
 7         }
 8         return q.poll();
 9     }
10 }

解法三: 又看到使用quickseleck 做的O(n)，二刷再试下。