大佬，救救萌新

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