我想问一下 为什么我这段链表（学生成绩排序输出）有的时候输出正常 有的时候死循环

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct student
{
char name[20];
float math;
};
struct node
{
struct student data ;
struct node next ;
};
struct node create( )
{
struct node head=(struct node)malloc(sizeof(struct node));
head->next=NULL;
return head;
}
//创建结点
struct node creatt(struct student data)
{
struct nodenewnode=(struct node*)malloc(sizeof(struct node));
newnode->data=data;
newnode->next=NULL;
return newnode;
}
void insert(struct node* head,struct student data)
{
struct node* newnode=creatt(data); //创建插入结点
newnode->next=head->next;
head->next=newnode;
}
void sortList(struct node* pList, int n)
{
//判断链表是否存在,是否为空
if (NULL==pList||NULL==pList->next )
{
printf ("您还没有添加学生信息\n");
exit(-1);
}
struct node p = pList->next;
//排序
int i,j;
for(i = 0; i < n-1; i++)
{
//第一轮排完之后，让指针重新指向头结点
p = pList->next;
for(j = 0; j < n-1-i; j++)
{
if(p->data.math > p->next->data.math)
{
///成绩
float tmp1 = p->data.math;
p->data.math = p->next->data.math;
p->next->data.math = tmp1;

        //学号
        char tmp2=p->data.name;
        p->data.name=p->next->data.name;
        p->next->data.name=tmp2;*/
         struct node *m=p;
         p=p->next;
         p->next=m;
     }
     p = p->next;
  }

}
}

void show(struct node * head)
{
struct node* pmove=head->next;
printf("name and math is:\n");
while(pmove)
{
printf("%s %6.2f\n",pmove->data.name,pmove->data.math);
pmove=pmove->next;
}
printf("\n");
}
int main()
{
struct node*list=create();
struct student info;
for(int i=0;i<3;i++)
{
printf("请输入学生姓名和成绩:\n");
scanf("%s%f",info.name,&info.math);
insert(list,info);
}
sortList(list,3);
show(list);
return 0;
}

这代码。。编译通不过吧。修改如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct student
{
    char name[20];
    float math;
};
struct node
{
    struct student data;
    struct node *next;
};
struct node* create()
{
    struct node *head = (struct node*)malloc(sizeof(struct node));
    head->next = NULL;
    return head;
}
//创建结点
struct node* creatt(struct student data)
{
    struct node *newnode = (struct node*)malloc(sizeof(struct node));
    newnode->data = data;
    newnode->next = NULL;
    return newnode;
}
void insert(struct node* head, struct student data)
{
    struct node* newnode = creatt(data); //创建插入结点
    newnode->next = head->next;
    head->next = newnode;
}

void sortList(struct node* pList)
{
    if (!pList||!pList->next) return;
    node* pre = pList,*cur=pre->next;
    while (cur->next)
    {
        node *p = pre, *q = cur;
        while (q->next)
        {
            if (q->data.math > q->next->data.math)
            {
                p->next = q->next;
                q->next = q->next->next;
                p->next->next = q;
            }
            p = p->next;
            q = p->next;
        }
        pre = pre->next;
        cur = pre->next;
    }
}

void show(struct node * head)
{
    struct node* pmove = head->next;
    printf("name and math is:\n");
    while (pmove)
    {
        printf("%s %6.2f\n", pmove->data.name, pmove->data.math);
        pmove = pmove->next;
    }
    printf("\n");
}

//销毁
void destroy(struct node * head)
{
    struct node *p = head, *del = NULL;
    while (p)
    {
        del = p;
        p = p->next;
        free(del);
    }
    head = NULL;
}
int main()
{
    struct node*list = create();
    struct student info;
    for (int i = 0; i < 3; i++)
    {
        printf("请输入学生姓名和成绩:\n");
        scanf("%s%f", info.name, &info.math);
        insert(list, info);
    }
    sortList(list);
    show(list);
    destroy(list);
}