HIndexII.java

package binary_search;

/**
 * Created by gouthamvidyapradhan on 11/12/2017.
 *
 * Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?
 * @see array.HIndex
 */
public class HIndexII {
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception{
        int[] A = {1, 1, 1, 1, 1, 15, 20};
        System.out.println(new HIndexII().hIndex(A));
    }

    public int hIndex(int[] citations) {
        if(citations.length == 0) return 0;
        int s = 0, e = citations.length;
        int ans = -1;
        while(s < e){
            int m = (s + e) >>> 1;
            int cit = citations.length - m;
            if(citations[m] > cit){
                if(ans < cit){
                    ans = cit;
                }
                e = m;
            } else{
                if(ans < citations[m]){
                    ans = citations[m];
                }
                s = m + 1;
            }
        }
        return ans;
    }

}