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;

}