为什么这个排序输出的会是一堆乱码？

Question

#include <stdio.h>#include <stdlib.h>#define LEN sizeof(struct student)struct student//定义结构体类型{    long num;    char  name[20];    float score;    struct student* next;};int n;int main()//程序{    struct student* creat(void);//动态链表函数声明    void output(struct student* head);//输出链表函数声明    int max();    //struct student* p0;    //p0 = creat();    //n = 0;    //output(p0);    creat();    max();    return 0;}struct student* creat(){    struct student* head, * p1, * p2;    p2 = 0;    head = NULL;    printf("请输入学生信息:学号  姓名  成绩:\n");    while (1)    {        p1 = (struct student*)malloc(LEN);        if (!p1)  return 0;        p1->next = NULL;        scanf_s("%ld %s %f", &p1->num, &p1->name, 20, &p1->score);        if (p1->num == 0)  break;        n++;        if (n == 1)            head = p1;        else            if (!p2) return 0;            else                p2->next = p1;        p2 = p1;    }    return head;}void output(struct student* head)//输出链表函数{    struct student* p;    p = head;    n = 0;    if (head != NULL)        do        {            printf("%ld,%s,%f\n", p->num, p->name, p->score);            p = p->next;            n++;        } while (p != NULL);}int max(){    struct student* p;    struct student head;    p =&head;    int i, j;    float a[LEN], t;    for (i = 0; i < (int)LEN; i++)        a[i] = p->score;    for (j = 0; j < (int)LEN; j++)        for (i = 0; i<(int)LEN - j; i++)            if (a[i] > a[i + 1])            {                t = a[i]; a[i] = a[i + 1]; a[i + 1] = t;            }    for (i = 0; i < (int)LEN; i++)        printf("%f", a[i]);    return 0;}