下面是我的java写的快排，过不了。。。```java import java.math.; import java.util.; import java.io.*;

public class Main {

public static void q_Sort(int[] book, int left, int right, int k) {
	if(right <= left)
		return;
	int head = left;
	int tail = right;
	int num = book[head];
	int m = head;
	while(head < tail) {
		while(tail > head && book[tail] > num)
			tail--;
		book[m] = book[tail];
		m = tail;
		while(head < tail && book[head] < num)
			head++;
		book[m] = book[head];
		m = head;
	}
	book[m] = num;
	if(m > k)
		q_Sort(book, left, m-1, k);
	else if(m < k)
		q_Sort(book, m+1, right, k);
}

public static void main(String[] args) {
	Scanner in = new Scanner(System.in);
	int n = in.nextInt();
	int k = in.nextInt();
	int[] book = new int[n];
	for(int i=0; i<n; i++)
		book[i] = in.nextInt();
	q_Sort(book, 0, n-1, k);
	System.out.println(book[k]);
}

}

我调用库函数Arrays.sort(book)也过不了，只能拿60分。想问问怎么搞啊