public static int activityNotifications(List expenditure, int d) { int notifications = 0; int[] count = new int[expenditure.stream().max(Integer::compareTo).get() + 1];

    for (int i = 0; i < d; i++) {
        count[expenditure.get(i)]++;
    }

    for (int i = d; i < expenditure.size(); i++) {
        double median = getMedian(count, d);

        if (expenditure.get(i) >= 2 * median) {
            notifications++;
        }

        count[expenditure.get(i - d)]--;
        count[expenditure.get(i)]++;
    }

    return notifications;
}

private static double getMedian(int[] count, int d) {
    int sum = 0;
    int mid1 = -1, mid2 = -1;
    boolean even = d % 2 == 0;
    int mid = d / 2;

    for (int i = 0; i < count.length; i++) {
        sum += count[i];

        if (even) {
            if (mid1 == -1 && sum >= mid)
                mid1 = i;
            if (mid2 == -1 && sum >= mid + 1) {
                mid2 = i;
                return (mid1 + mid2) / 2.0;
            }
        } else {
            if (sum > mid)
                return i;
        }
    }
    return 0;
}