3 - Two Pointers Algorithm

5. Kth Largest Element (quick sort的变种)

https://www.lintcode.com/problem/kth-largest-element/description?_from=ladder&&fromId=1

public class Solution {
    /**
     * @param n: An integer
     * @param nums: An array
     * @return: the Kth largest element
     */
    public int kthLargestElement(int n, int[] nums) {
        // write your code here
        quickSort(nums, 0, nums.length - 1);
        int len = nums.length;
        return nums[len - n];
    }

    public void quickSort(int[] nums, int left, int right) {
        if(left >= right) {
            return;
        }
        int mid = nums[left + (right - left) / 2];
        int l = left, r = right;
        while(l <= r) {
            while(l <= r && nums[l] < mid) {
                l++;
            }
            while(l <= r && nums[r] > mid) {
                r--;
            }
            if(l <= r) {
                int temp = nums[l];
                nums[l] = nums[r];
                nums[r] = temp;
                l++;
                r--;
            }
        }
        quickSort(nums, left, r);
        quickSort(nums, l, right);
    }
}