如何在C中初始化未知大小的数组

我正在为C语言编程课的入门做作业。

我需要编写一个程序，该程序查看int未知大小的数组（我们将获得一个初始化程序列表作为要使用的测试用例），并确定该数组中的所有重复项。

为了确保不会发现已经重复的元素，我想对原始元素使用一个并行数组，该数组将保存所有重复元素的数量。

我需要此数组的大小与原始数组的大小相同，当然，在提供初始化程序列表之前，我们当然并不真正知道它。

我尝试使用sizeof()来实现此目的，但Visual Studio表示这是错误的，因为可变大小（const int size = sizeof(array1);）不一致。我没有正确使用sizeof吗？还是这种逻辑有缺陷？

也许还有另一种方法可以解决这个问题，但是我还没有想出一个办法。

这是下面包含的代码，希望注释不要太难阅读。

// Dean Davis
// Cs 1325
// Dr. Paulk
// Duplicates hw

#include <stdio.h>

int main()
{
    int array1[] = {     0,0,0,0,123,124,125,3000,3000,82,876,986,345,1990,2367,98,2,444,993,635,283,544,    923,18,543,777,234,549,864,39,97,986,986,1,2999,473,776,9,23,397,15,822,1927,1438,1937,1956,7, 29,- 1 };
const int size = sizeof(array1);
int holdelements[size]; 
int a = 0; // counter for the loop to initialize the hold elements array
int b = 0; // counter used to move through array1 and be the element number of the element being tested
int c = 0; // counter used to move through holdelements and check to see if the element b has already been tested or found as duplicates
int d = 0; // counter used to move through array1 and check to see if there are any duplicates 
int e = 0; // counter used to hold place in hold element at the next element where a new element number would go. sorry if that makes no sense
int flag = 0; // used as a boolian to make sure then large while loop ends when we reach a negative one value.
int flag2 = 0; // used as a boolian to stop the second while loop from being infinite. stops the loop when the end of hold elements has been reached
int flag3 = 0; // used to close the third while loop; is a boolian
int numberofduplicates=0;// keeps track of the number of duplicates found

for (a; a < size; a++)
{
    if (a == (size - 1))
        holdelements[a] = -1;
    else
        holdelements[a] = -2;
}

while (!flag)
{
    flag2 = 0;
    flag3 = 0;
    if (array1[b] == -1)
        flag = 1;
    else
    {
        while ((!flag) && (!flag2))
        {
            if (holdelements[c] == -1)
                flag2 = 1;
            else if (array1[b] == holdelements[c])
            {
                b++;
                c = 0;
                if (array1[b] == -1)
                    flag = 1;
            }
        }
        while (!flag3)
        {
            if (array1[d] == -1)
                flag3 = 1;
            else if (array1[b] == array1[d] && b != d)
            {
                printf("Duplicate of %d, index %d, was found at index %d.\n", array1[b], b, d);
                holdelements[e] = d;
                d++;
                e++;
                numberofduplicates++;
            }
        }
    }
    b++;
}
printf("Total Duplicates Found: %d\n", numberofduplicates);
return 0;
}