10_15

#define  NUM  4
#define  SUB_NUM 5

/*定义全局变量结构体*/
static struct  student
    {  char  name[20];
       char  stu_id[5];          /* format 000 */
       float subject_point[SUB_NUM];  /* five subject point */
    }stu[NUM] ={{"lili","001",34,18,73,12,10},
    {"tata","002",24,36,72,72,90},
    {"haha","003",90,90,90,90,90},
    {"qiqi","004",65,56,87,52,90}};

#include
#include
void main()
{
    float Average_sub(int );
    struct student *find(char *);
    int Unpass(void);
    float Average_per(char *);

//    struct student *s;     /*stu结构体指针*/

//   int i ;
      int course_code;
      float average;
      char  student_id[10];
      float average_person;

//    printf("input the student infomation\n");
//    s = stu;

/************************************************************************** 
    for(i = 0;i < NUM; i++){
        scanf("%d%s",s->name,s->stu_id);
        for(j = 0;j < SUB_NUM; j++)  scanf("%f",&s->subject_point[j]);
        s++;
    }
**************************************************************************/
    printf("\n");
    printf("Calculated the average performance of a class\n");
    printf("Please,input the course code(eg: 1,2,3,4,5)\n");
    scanf("%d",&course_code);
    average = Average_sub(course_code);
 printf("\n");
    printf("the course %d performance is%f\n",course_code,average);
    printf("\n");
    printf("to find the student failed to pass two or more courses\n");
    Unpass();
    printf("\n");
    printf("Calculate the average performance of a person\n");
    printf("Please,input the student id(format 000)\n");
    scanf("%s",student_id);
 printf("\n");
    average_person = Average_per(student_id);
    printf("the student %s's average is %f\n",student_id,average_person);

    getchar();
}

/***************************************************************************
*function name:求某一门课的平均成绩
*input argument:课程代码（1，2，3，4，5）
*output argument: average grade
****************************************************************************/
float Average_sub(int sub_number)
{
    int i;
    float sum = 0;
    int sub_num;
    struct student *p;

    p = stu;
    sub_num = sub_number;
 if(sub_num<1 || sub_num>5){
  printf("input is error");
  return 0;
 }

    sub_num--;       /* 课程代码减一(从零开始)*/

    for(i=0;i < NUM; i++)
    {
        sum = p->subject_point[sub_num] + sum;
        p++;
    }                             /*sum*/

    sum = sum / NUM;              /*ave*/
    return sum;

}

/*****************************************************
*function:查找匹配
*note:简单查询
*intput:student ID
*output:所在数组的位置（结构体指针）
****************************************************/
struct student *find(char *id )
{
//   int i = 0;
   struct student *p;

   p = stu ;      /*数组入口赋值给p*/

   while (strcmp(id,p->stu_id))      /*strcmp比较两个字符串相等,相等返回0*/
    {
        if(p < stu + NUM)
            p++;
        else
        {
            printf("the input is error\n"); /*查找完毕未发现匹配项*/
            break;
        }
    }
   
    return p;                    /*返回指针p*/

}
                                         /*问题：id只是字符串的首地址*/

/***********************************************
*function:求个人平均成绩
*input argument:student ID?
*output argumnet：个人平均成绩
***********************************************/
float Average_per(char *st_id)
{
    int i;
    struct student *p;
    float av = 0;
    char *ch;

    ch = st_id;
    p = find(ch);
 if(p >= (stu + NUM)) return 0;
    for(i = 0; i < SUB_NUM; i++)
    {
        av = av + p->subject_point[i];
    }   /*sum*/
    av = av/SUB_NUM;      /*averaging*/
    return av ;
}

/***********************************************
*function name:找出两门及以上不及格的学生
*input argumnet: void
*output argument: student number
*notice:输出学生学号
************************************************/
int Unpass(void)
{
    int count;
    int i,j;
    struct student *p;

    p = stu;

    for (i = 0; i < NUM; i++)
    {
        count = 0;
        for (j = 0; j < SUB_NUM; j++)
  {
   if (count >= 2){
                    printf("the student NO.%s\n",p->stu_id);
                    break;         //充分体现了for和continue的区别（continue 跳出if循环，break跳出最近的第一个for循环）
   }
            if (p->subject_point[j] < 60) count++;  
        }
        p++;
    }
    return 0;
}

/************************************************************
//经验：
//字符串，最好用数组表式（char st[10]）,不建议使用指针char *st。
//scanf("%s",student_id);
//printf("\n");
//scanf("%s\n",student_id) 此句和上面两句比较在调试上出问题。
*************************************************************/