c - 如何在 C 中的数组内创建没有预定义大小的数组？

Question

我想在 C 中的数组中创建数组，而无需在数组中预定义数量的字符或输入。 以下是我的代码:

{
    int noOfStudents,noOfItems;
    int *grades;
    int i;
    char a[];
    printf("Please enter number of students\n");
    scanf("%d", &noOfStudents);
    printf("Please enter number of items\n");
    scanf("%d", &noOfItems);

    for (i = 0; i < noOfStudents; i++)
    {
        a[i] = (int *)malloc((sizeof(int))*noOfItems);
    }

我遇到了一个错误

c(2133): 'a': unknown size

如何通过malloc在数组中成功创建数组？

Answer 1

您可以使用 VLA (Variable length array) .

您需要重新排列代码，例如

int noOfStudents = -1, noOfItems = -1;
int *grades;                                //is it used?
int i;

printf("Please enter number of students\n");
scanf("%d", &noOfStudents);

//fail check

int *a[noOfStudents];             // this needs to be proper.

//VLA

printf("Please enter number of items\n");
scanf("%d", &noOfItems);

//fail check

for (i = 0; i < noOfStudents; i++)
{
    a[i] = malloc(noOfItems * sizeof(a[i]));   //do not cast
}