here is my code and it always output -1 and I didn’t know why. any help?
Input
The first line contains an integer t (1≤t≤104) — the number of test cases.

The first line of each test case contains an integer n (1≤n≤2⋅105) — the length of the array.

The second line of each test case contains n integers a1,a2,…,an (1≤ai≤n) — the elements of the array.

It is guaranteed that the sum of n over all test cases does not exceed 2⋅105.

Output
For each test case, print any value that appears at least three times or print -1 if there is no such value.

#include <stdio.h>
#include <stdlib.h>
int main()
{
    int n, size,*arr, *frr,count,*ptr,g,s;
    scanf("%d", &n);
    ptr = (int*)malloc(n * sizeof(int));
    for (int i = 0;i < n; i++)
    {
        scanf("%d",&size);
        arr = (int*)malloc(size * sizeof(int));
        frr = (int*)malloc(size * sizeof(int));
        for(int j = 0; j < size; j++)
            {
                scanf("%d",arr+j);
                *(frr + j) = -1;
            }
        if(size >= 3)
        {
            for (g = 0; g < size ; g++)
            {
                count=1;
                for(s = g + 1; s < size;s++)
                {
                    if(*(arr + g) == *(arr + s))
                    {
                        count++;
                        *(frr+s) = 0;
                    }             
                }
                if(*(frr+g) != 0 )
                {
                    *(frr+g) = count;
                }

                if(*(frr+g) >= 3)
                {
                    *(ptr+i) = *(arr + g);
                }else
                {
                    *(ptr+i) = -1;
                }
                
            }  
        }else
        {
            *(ptr+i) = -1;
        }
        
        free(arr);
        free(frr);

    }
    for(int j = 0;j<n;j++)
    {
        printf("%d\n",*(ptr+j));
    }
}

>Solution :

The problem is that you set *(ptr+i) to -1 for each element of the array. This means that a later element of the array that is not repeated three times will reset *(ptr+i) to -1.

Change this

            if(*(frr+g) >= 3)
            {
                *(ptr+i) = *(arr + g);
            }
            else
            {
                *(ptr+i) = -1;
            }

to this

            if(*(ptr+i) == -1 && *(frr+g) >= 3)
            {
                *(ptr+i) = *(arr + g);
            }

and at the beginning add this

ptr = (int*)malloc(n * sizeof(int));
for (int i = 0;i < n; i++)
{
    *(ptr + i) = -1;

But as has already been said in the comments you do not need either the ptr array or the frr array. You only run one test at a time so there is no need to keep all the test results before you print any of them out. And you only need to save the frequency of the current element you are testing, so you don’t need an array for that either.

And make your code readable, change *(arr + g) to arr[g]. They both work exactly the same.