Leetcode: Kth Largest Element in an Array

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.

 1 public class Solution {
 2     public int findKthLargest(int[] nums, int k) {
 3         int len = nums.length;
 4         return findKthSmallest(nums, 0, len-1, len-k+1);
 5     }
 6     
 7     public int findKthSmallest(int[] nums, int start, int end, int k) {
 8         int l = start;
 9         int r = end;
10         int pivot = end;
11         while (l < r) {
12             while (l<r && nums[l] < nums[pivot]) {
13                 l++;
14             }
15             while (l<r && nums[r] >= nums[pivot]) {
16                 r--;
17             }
18             if (l == r) break;
19             swap(nums, l, r);
20         }
21         swap(nums, l, pivot);
22         if (l+1 == k) return nums[l];
23         else if (l+1 < k) return findKthSmallest(nums, l+1, end, k);
24         else return findKthSmallest(nums, start, l-1, k);
25     }
26     
27     public void swap(int[] nums, int l, int r) {
28         int temp = nums[l];
29         nums[l] = nums[r];
30         nums[r] = temp;
31     }
32 }