どのように私はグレードとして0（ゼロ）を無視することはできません？

Question

int main(){ 

    char students_number[30], students_grade[30]; 
    char *number, *value; 
    int flag=0, students, i, grade, a=0, b=0, c=0, d=0, f=0; 
    float sum=0; 

    while(flag==0) // This while loop exist just because to run program until the number of students will be given correct.. 
    { 

     printf("Please enter the number of students (It must be between 1-100): "); 
     scanf("%s",&students_number); // This scanf gets the number of students as an array instead of integer because the number which was given needs to be checked.. 
     students = strtol(students_number, &number, 10); // strtol is a function of stdlib.h and checks the variable is whether int or not for this program.. 

     if(students<=100 && students>0) 
     { 
      for(i=1;i<=students;i++) 
      { 
       printf("Please enter %d. student's grade (in integer form):",i); 
       scanf("%s",&students_grade);// This scanf gets the number of students as an array instead of integer because the number which was given needs to be checked.. 
       grade = strtol(students_grade, &value, 10); // This line checks the grade which was given is integer or not by using strtol which is in the stdlib.h.. 

       if(grade<0 || grade>100 || grade=='\0') 
       { 
        printf("The grade of the student was given incorrect!\n"); 
        i--; // To make the for loop which is on the 25th line work again until the grade will be given correct.. 
       } 
       else 
       { 
        if(grade<=50 && grade>=0) // This if and else if commands work for to count how many f,d,c,b and a are exist.. 
         f++; 
        else if(grade<=60 && grade>=51) 
         d++; 
        else if(grade<=73 && grade>=61) 
         c++; 
        else if(grade<=85 && grade>=74) 
         b++; 
        else if(grade<=100 && grade>=86) 
         a++; 
        sum += grade;    
       } 
      } 
      sum /= students; // This command divides the sum of the grades to number of the students to get the average results in the class.. 

      printf("\nThe average result of the class is %.2f..\n",sum); 
      printf("\nThe letter form of the all results are:\nNumber of F: %d\nNumber of D: %d\nNumber of C: %d\nNumber of B: %d\nNumber of A: %d\n",f,d,c,b,a); 
      flag = 1; // As it was mentioned before, this commands exist to break the while loop because the program was done successfully.. 
     } 
     else // This if command controls the number of students wheter was given right or not.. 
     { 
      printf("Please enter a proper number of students.\n"); 
      flag = 0;   
     } 
    } 
    return 0; 
} 

こんにちは、これは私の最初の質問です。結果の平均を計算するプログラムを作成しなければなりませんでした。しかし、グレードとして0（ゼロ）を入力すると、int型以外のすべての型を除外しようとしたため、許容されません。

どうすればこの問題を解決できますか？

Answer 1

あなたは数を読み、scanfが正しくその仕事をしていることを確認するためにscanfを使用することができます。

man scanfから：

戻り値 これらの関数は、入力項目の数が正常にマッチした戻り、割り当てられた数よりも少なくなる可能性があり、早期のマッチングに失敗した場合でもゼロになる可能性があります。

だから、あなたは0等級を読み取ることができないようにif (value == '\0')を記述することなく、scanfで整数を読んだことを確認することができます...

for(i=1;i<=students;i++) 
{ 
    int ok; 

    printf("Please enter %d. student's grade (in integer form):",i); 

    /* read line from input. Why using fgets instead of scanf directly? See http://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html*/ 
    if (NULL == fgets(students_grade, sizeof students_grade, stdin)) 
    { 
     perror("fgets"); 
     exit(1);    
    } 

    /* **try** to parse what have been read */ 
    ok = sscanf(students_grade, "%d", &value); 

    /* check that scanf has done its work */ 
    if (1 != ok) 
    { 
     printf("The grade of the student was given incorrect!\n"); 
      i--; // To make the for loop which is on the 25th line work again until the grade will be given correct.. 

    } 
    else 
    { 
     if(grade<=50 && grade>=0) // This if and else if commands work for to count how many f,d,c,b and a are exist.. 
     f++; 
     /* ... */ 
    } 

私もこの記事を読むためにあなたをアドバイス

： http://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html。