Can't be done for C, Might as well share my solution:

int compare(const void *a, const void b) { return ((const int *)a - *(const int *)b); }

int main() { int cases; scanf("%d", &cases); for (int k = 0; k< cases; k++) { int n; scanf("%d", &n); int *arr = malloc(n * sizeof(int)); int *final = malloc(n * sizeof(int));
for (int i = 0; i < n; i++) { scanf("%d", &arr[i]); }

    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    qsort(arr, n, sizeof(int), compare);
    for (int i = 0; i < n/2; i++) {
        final[i] = arr[i];
        final[n - i- 1] = arr[n/2+i];
    }
    final[n/2] = arr[n-1];
    for (int i = 0; i < n; i++) {
        printf("%d ", final[i]);
    }
    printf("\n");
}
return 0;

}

Too stiff check.
In C++11 it allows the following set of changes:

06: int mid = (n - 1) / 2;
10: int ed = n - 2;
14:   ed = ed - 1;

but does allow the following:

07: ; // dropped first swap
09: int st = mid - 1;
14:   ed = ed - 1;

Though the resulting output is exactly the same.

This one in C# asks to create to whole class but it fails... Am I getting negatives cuz of performance?

class Solution {
    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        int queries = Convert.ToInt32(Console.ReadLine());
        int arrLength = Convert.ToInt32(Console.ReadLine());
        string[] arrStr = Console.ReadLine().Split(' ');
        int[] arr = new int[arrLength];
        int[] res = new int[arrLength];

        for (int count = 0; count < arrStr.Length; count++)
        {
            int item = Convert.ToInt32(arrStr[count]);
            arr[count] = item;
        }

        arr = arr.OrderBy(x => x).ToArray();

        for (int index = 0; index < arrLength; index++)
        {
            res[index] = arr[index < (arrLength - 1) / 2 ? index : (arrLength - index) + 2];
        }

        Console.WriteLine(String.Join(" ", res).Trim());
    }
}

Typescript doesn't work, its missing the actual code...

The function isn't there when using R, just indicates where to write the code.