static int[] leftRotation(int[] a, int d) {
        for (int i = 0, j = a.length - 1; i < j; i++, j--)
            swap(a, i, j);

        d %= a.length;

        if (d > 0) {
            d = a.length - d;

            for (int i = 0, j = d - 1; i < j; i++, j--)
                swap(a, i, j);

            for (int i = d, j = a.length - 1; i < j; i++, j--)
                swap(a, i, j);
        }

        return a;
    }

    private static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }