快速排序（效果最好）

import java.util.*;

public class Solution {
    public int findKth(int[] a, int n, int K) {
        // write code here
        quickSort(a, 0, n - 1);
        return a[n - K];
    }

    public void quickSort(int[] arr, int left, int right) {
        if (left >= right) return;
        int i = left;
        int j = right;
        int tmp = arr[left];
        while (i < j) {
            while (i < j && arr[j] >= tmp) j--;
            while (i < j && arr[i] <= tmp) i++;
            if (i < j) {
                int t = arr[i];
                arr[i] = arr[j];
                arr[j] = t;
            }
        }
        arr[left] = arr[i];
        arr[i] = tmp;
        quickSort(arr, left, i - 1);
        quickSort(arr, i + 1, right);
    }
}