[LintCode] 第K大元素 Kth Largest Element

在数组中找到第k大的元素。
样例
给出数组 [9,3,2,4,8]，第三大的元素是 4
给出数组 [1,2,3,4,5]，第一大的元素是 5，第二大的元素是 4，第三大的元素是 3，以此类推
挑战
要求时间复杂度为O(n)，空间复杂度为O(1)

Find K-th largest element in an array.
Example
In array [9,3,2,4,8], the 3rd largest element is 4.
In array [1,2,3,4,5], the 1st largest element is 5, 2nd largest element is 4, 3rd largest element is 3 and etc.

Challenge
O(n) time, O(1) extra memory.

时间复杂度O（nlogn）?

class Solution {    /*     * @param k : description of k     * @param nums : array of nums     * @return: description of return     */    public int kthLargestElement(int k, int[] nums) {        if(null == nums ||k <= 0 || nums.length < k) return Integer.MIN_VALUE;        kthMax(nums, 0, nums.length-1, k);        return nums[k-1];    }    public void kthMax(int[] nums, int left, int right, int k) {        int mid = partition(nums, left, right);        if(mid == k-1) return;        if(mid > k-1)            kthMax(nums, left, mid-1, k);        else            kthMax(nums, mid+1, right, k);    }    public int partition(int[] nums, int left, int right) {        int temp = nums[left];        while(left < right) {            while(left < right && nums[right] <= temp)                right--;            nums[left] = nums[right];            while(left < right && nums[left] > temp)                left++;            nums[right] = nums[left];        }        nums[left] = temp;        return left;    }};