问一下为什么我的这个数据结构有问题 在主函数第一个for循环的地方

 #include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
//顺序表的训练 以学生记录为基础
#define MAXNAME 30
#define MAXPERSON 20
#define bool int
#define false 0
#define true  1
struct student
{
    char s_name[MAXNAME];
     int s_num;
    char s_sex;
    char s_class[MAXNAME];
};
struct node
{
    struct student std[MAXPERSON];
    int length ;
    int listsize ;
};
void InitList(struct node **list)//建立顺序表
{
    *list = (struct node*)malloc(sizeof(struct node));
    if (!*list)
        return ;
    else
    {
        (*list)->length = 0;
        (*list)->listsize = MAXPERSON;
    }
}
void ClearList(struct node *list)//清空顺序表
{
    if (list)
    {
        free(list);
        return;
    }
    printf("the list is empty \n");
    return;
}
bool ListEmpty(struct node *list)//返回是否为空
{
    if (list)
        return false;
    else
        return true;
}
int ListLength(struct node *list)//返回线性表的长度
{
    if (list)
        return list->length;
    else
        return 0;
}
bool GetElem(struct node *list, int i, struct student *e)//用e保存返回的元素
{
    if (list)
    {
        if (i <= list->length && i >= 1)
        {
            *e = list->std[i - 1];//返回第i个数据元素
            return true;
        }
    }
    return false;
}
int main(void)
{
    struct node *List=NULL;
    InitList(&List);
    ClearList(List);
    int j = 0,i=0;//下标
    for (;i <3;i++)
    {
        struct student temp;
        printf("please input student's name num sex class \n");

        if (fscanf(stdin,"%s %d %c %s", temp.s_name, &temp.s_num, &temp.s_sex, temp.s_class)== 4)
        {
             List->std[j];//此处有错
            (List->length)++;
            j++;
        }

            printf("input error\n");
    }
    struct student temp;
    if (GetElem(List,1,&temp))
        printf("%s %d %c %s\n", temp.s_name, temp.s_num, temp.s_sex, temp.s_class);
    else
        printf("not exist the element\n");
}

List->std[j];//此处有错

这个语句是什么鬼，。。。。。。有作用吗？