#include<stdio.h>
#include<string.h>
struct Student
{
    char num[6];
    char name[10];
    int math;
    int english;
    int general;
};
struct Student stu[100]={{"05001","Jam",78,68,146},{"05002","Bill",80,98,178},{"05003","Bob",82,83,165},{"05004","Sam",69,82,151},{"05005","Steven",94,83,177}};
void main()
{
    int i,j;
    for(i=0;i<100;i++)
        if(stu[i].num[0]==NULL)
            j=i;
        printf("%d",j);
}

我本意是求出j=5,结果却是j=99。
求指点

找到之后 立即break退出循环  否则你保存的变量值 就被覆盖了啊

#include<stdio.h>
#include<string.h>
struct Student
{
    char num[6];
    char name[10];
    int math;
    int english;
    int general;
};
struct Student stu[100]={{"05001","Jam",78,68,146},{"05002","Bill",80,98,178},{"05003","Bob",82,83,165},{"05004","Sam",69,82,151},{"05005","Steven",94,83,177}};
void main()
{
    int i,j;
    for(i=0;i<100;i++)
    {
        if(stu[i].num[0]==NULL)
            j=i;
        break;
    }
        printf("%d",j);
}

不知道这么结果变为一个很大的负数

那个 J=I  BREAK 都从属于if语句  大括号 哪里去了

可以了，非常感谢！

结贴

#include<stdio.h>
#include<string.h>

struct Student
{
    char num[6];
    char name[10];
    int math;
    int english;
    int general;
};

struct Student stu[100]={
                            {"05001","Jam",78,68,146},
                            {"05002","Bill",80,98,178},
                            {"05003","Bob",82,83,165},
                            {"05004","Sam",69,82,151},
                            {"05005","Steven",94,83,177}
                        };

void main()
{
    int i = 0;
    int j = 0;
    for(i=0;i<100;i++)
    {
        if(stu[i].num[0] == NULL)
        {
            j = i;
            printf("%d\n",j);
        }
    }   
        
}
---------
你的需求是打印出，空数组的个数？
还是打印出 空数组的下标呢？？
这个是打印的所有空数组的下标

打印下标

C＋＋是不是C结构体的引申发展

斑竹这些分就算了吧。。你那么多分了。。让我们分分