LeetCode - H-Index II

public int hIndex(int[] citations) {
    int len = citations.length, left = 0, right = len - 1;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (citations[mid] == len - mid) return len - mid;
        else if (citations[mid] > len - mid) right = mid - 1;
        else left = mid + 1;
    }
    return len - left;
}