这个程序最后是把连接好的两个链表按照num的值排了序，但是我的这个代码没有排序，我试着排了序但排不出来，所以下面这个代码没有排序的代码，还请大神教教我

#include<stdio.h>
#include<malloc.h>

#define LEN sizeof(struct student)

int sum = 0;
/* User Code Begin(考生可在本行后添加代码，定义程序中使用的结构体类型、声明自定义函数的原型，行数不限) */
struct student
{
    int num;
    int score;
    struct student *next;
};

struct student *creat(void);
struct student *merge(struct student *ahead, struct student *bhead);

/* User Code End(考生添加代码结束) */

/* print以规定的格式完成遍历显示指定的链表 */
void print(struct student *Head);

int main(void)
{
    struct student *ah, *bh, *ac;
    
    printf("创建链表A，请输入学号及成绩(均输入为0时表示停止)：\n");
    ah = creat();
    printf("\n创建链表B，请输入学号及成绩(均输入为0时表示停止)：\n");
    bh = creat();

    printf("\n链表A：");
    print(ah);
    printf("\n链表B：");
    print(bh);
    
    ac = merge(ah, bh);
    printf("\n两个链表共有%d个人\n链表C：", sum);
    print(ac);
    
    return 0;
}

void print(struct student *Head)
{
    while (Head != NULL)
    {
        printf("%d,%d  ", Head->num, Head->score);
        Head = Head->next;
    }
}

/* User Code Begin(考生在此后完成自定义函数的设计，行数不限) */
struct student *creat(void)
{
    struct student *head;
    struct student *p1, *p2;
    int num = 0;
    
    sum++;
    printf("学生 %d: ", sum);
    p1 = p2 = (struct student *)malloc(LEN);
    scanf("%d %d", &p1->num, &p1->score);
    head = NULL;
    while (p1->num != 0)
    {
        num++;
        sum++;
        if (num == 1)
        {
            head = p1;
        }
        else
        {
            p2->next = p1;
            p2 = p1;
        }
        printf("学生 %d: ", sum);
        p1 = (struct student *)malloc(LEN);
        scanf("%d %d", &p1->num, &p1->score);
    }
    p2->next = NULL;
    sum--;

    return head;
}

struct student *merge(struct student *ahead, struct student *bhead)
{
    struct student *p1,*p2=NULL;
    int i=0;
    
    p1 = ahead;
    if (sum == 0)
    {
        return NULL;
    }
    else if (ahead == NULL)
    {
        return bhead;
    }
    else if (bhead == NULL)
    {
        return ahead;
    }
    else
    {
        while (p1->next != NULL)
        {
            p1 = p1->next;
        }
        p1->next = bhead;
    }
    
    return ahead;
}