Kth Largest Element

class Solution {
    /*
     * @param k : description of k
     * @param nums : array of nums
     * @return: description of return
     */
    public int kthLargestElement(int k, int[] nums) {
        // write your code here
        if (nums  == null || nums.length == 0) {
            return -1;
        }
        return quickSelect(nums, 0, nums.length - 1, k);
    }
    
    private int quickSelect(int[] nums, int start, int end, int k)  {
        if (start == end) {
            return nums[start];
        }
        
        int pivot = nums[start + (end - start) / 2];
        int left = start;
        int right = end;
        while (left <= right) {
            while (left <= right && nums[left] > pivot) {
                left++;
            }
            while (left <= right && nums[right] < pivot) {
                right--;
            }
            if (left <= right) {
                int tmp = nums[left];
                nums[left] = nums[right];
                nums[right] = tmp;
                left++;
                right--;
            }
        }
        
        if (start + k - 1 <= right) {
            return quickSelect(nums, start, right, k);
        }
        if (start + k - 1 >= left) {
            //This is the k -(left - start)th of the last part
            return quickSelect(nums, left, end, k - (left - start));
        }  
        
        return nums[right + 1];
    }
};