求教一下关于链表的输入

Question

求教一下关于链表的输入；

#include<stdio.h>
#include <malloc.h>
#include<stdlib.h>
#include<windows.h>
#include<time.h>
#define LEN sizeof(struct Student)
int c_num()
{
    static int i = 1; int a;
    a = 2019051000 + i;
    i = i + 1;
    return a;
}

struct Student
{
    int num;
    struct Student* next;
};
int n;
struct Student* creat(void)
{
    struct Student* head;
    struct Student* p1, * p2;
    n = 0;
    p1 = p2 = (struct Student*)malloc(LEN);
    p1->num = 2019051110;
    //scanf("%d", &p1->num);
    head = NULL;
    while (p1->num != 0)
    {
        n = n + 1;
        if (n == 1)head = p1;
        else p2->next = p1;
        p2 = p1;
        p1 = (struct Student*)malloc(LEN);
        p1->num = c_num();
        //scanf("%d", &p1->num);
    }
    p2->next = NULL;
    return (head);
}
int main()
{
    struct Student* pt;
    pt = creat();
    printf("num=%d", pt->num);
}

为什么这样会有nullptr的报错，而使用//里的scanf函数就没有问题？
请各位不吝赐教

Answer 1

2019051000
这个数字太大，超过int范围
学号、电话、邮政编码、身份证号等这些虽然是数字，但是不参与四则运算的（两个学号相加相减没有意义），应该使用字符串表示。