H-Index II

class Solution {
    public int hIndex(int[] citations) {
        int L=0;
        int R=citations.length;
        while (L<R){
            int mid = (R+L)/2;
            int number = citations.length - mid;
            if(number == citations[mid]){
                return number;
            }
            if(number < citations[mid]){ 
                R = mid;
            }
            else{
                L = mid+1;
            }
        }
        return citations.length - L;
    }   
}