Question

我正在编写这个成绩簿程序，并且在我的get_data函数的最后发生了无限循环我无法弄清楚为什么它不会退出循环。以下是我应该运行的示例：

ID, NAME, GRADE
2442
Kapowski, Kelly
87 99 100 87 88 -99
1254
Slater, A.C.
90 100 -99
8742
Morris, Zack
77 65 50 80 66 -99

代码：

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

#define MAX_NAME 50
#define MAX_SCORES 20
#define MAX_FILE_NAME 100

typedef struct {
    char name[MAX_NAME];
    int id;
    double scores[MAX_SCORES];
    int num_scores;

} student_t;

double student_average (student_t student);
FILE * get_data_file();
void get_data(student_t students[], int num_students, FILE *input_file);
void sort_student_array(student_t students[], int num_students);
int find_index_of_next(const student_t students[], int num_elements, int start_index);
void display_data(const student_t students[], int num_elements);

int main()
{
    student_t *students;
    FILE *input_file;
    int num_students;


    input_file = get_data_file();

    fscanf (input_file, "%d", &num_students);

    students = (student_t *)calloc(num_students, sizeof(student_t));

    get_data(students, num_students, input_file);

    sort_student_array(students, num_students);

    display_data(students, num_students);

    free(students);

    return 0;
}

double student_average (student_t student)
{
    double average,
           total;
    int count;

    for (count = 0; count < student.num_scores; count++)
        total += student.scores[count];

    average = total / student.num_scores;

    return average;
}

FILE * get_data_file()
{
    int valid = 0;
    char file_name[MAX_FILE_NAME];
    FILE *in_file;

    printf("Welcome to the automated grade book program. Version 2.0\n");

    do
    {

        printf ("Enter student data filename:");
        scanf ("%s", file_name);
        in_file = fopen (file_name, "r");

        if (in_file != NULL)
        {
            valid = 1;
        }
        else
        {
            printf ("Unable to open file %s. Try again.\n", file_name);
        }
    } while (!valid);
    return in_file;
}

void get_data(student_t students[],
              int num_students,
              FILE *input_file)
{
    int count;
    int count2;
    student_t student;
    double value;

    for (count = 0; count < num_students; count++)
    {

        fscanf (input_file, "%d\n", &student.id);

        fgets (student.name, MAX_NAME, input_file);

        student.name[strlen(student.name)-1] = '\0';

        fscanf(input_file, "%lf", &value);

/*
/I am getting stuck right HERE
*/
        count2 = 0;
        while (value != -99)
        {
            student.scores[count2] = value;
            fscanf(input_file, "%lf", &value);
            count2++;             
        }

        student.num_scores = count2;

        students[count] = student;

    }
}

Answer 1

我打赌你文件中的-个标志之一实际上是一个不同的角色。这会导致fscanf失败，value永远不会设置，并且您有一个无限循环。您应该检查转换函数的返回值 - 例如

if(fscanf(input_file, "%lf", &value) !=1) break;

它不会是第一个带有棘手扭曲的任务......

无法弄清楚连续循环有什么问题

1 个答案: