Write a program that uses an array to hold course grades.
Array is initialized to zero in the beginning.
Program then asks user to enter student number and then asks
user to enter grade for the student in question.
Program must check that array bounds are not violated.
User terminates input by entering -1 as student number.
In the end program calculates and prints the average of
course grades.
有输入好多学生的学号和成绩，然后当学号为负时输出成绩平均值
我的问题是，如果学号相同，即想要update一个学生的成绩是，应该怎么做呢

#include <stdio.h>
#include<stdlib.h>
typedef struct student
{
    int no;
    float score;
    struct student *next;
}ST;

int isdif(ST *,int );

void main()
{
    int n,i=0;
    float sum=0;
    ST *p=NULL, *h=NULL;
     
    printf("请输入学生信息，以输入学号-1结束.\n");
    printf("请输入学生学号：");
    scanf("%d",&n);
    while(n != -1)
    {
        if(isdif(h,n))
        {
            i++;
            p=(ST*)malloc(sizeof(ST));
            p->no=n;
            printf("请输入学生成绩：");
            scanf("%f",&p->score);
            sum += p->score;
            p->next=h;
            h=p;
        }
        system("cls");
         printf("请输入学生学号：");
         scanf("%d",&n);
    }
    printf("%.2f",sum/i);
}

int isdif(ST *head, int n)
{
    ST *p=head;
   
    while(p && p->no != n)
    {
        p=p->next;
    }
    if(p) return 0;
    else return 1;
}
试着写了下，不知识否可以。发现问题找我。

2不2

学号有可能相同？

什么是key-word

[ 本帖最后由 Devil_W 于 2010-2-21 14:35 编辑 ]

作业题？

从新给该学生的成绩赋值啊