leetcode HIndex
z
 2019-04-09 10:36:27   
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public class HIndex {
  public static int solution(int[] citations){
    /**
     *  citations: sorted arrays
     *
     * Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index.
     *
     * According to the definition of h-index on Wikipedia: "A scientist has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each."
     *
     * Example:
     *
     * Input: citations = [0,1,3,5,6]
     * Output: 3
     * Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had
     *              received 0, 1, 3, 5, 6 citations respectively.
     *              Since the researcher has 3 papers with at least 3 citations each and the remaining
     *              two with no more than 3 citations each, her h-index is 3.
     * Note:
     *
     * If there are several possible values for h, the maximum one is taken as the h-index.
     *
     * Follow up:
     *
     * This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
     * Could you solve it in logarithmic time complexity?
     */
    int n = citations.length;
    int left = 0;
    int right = n;
    while(left <= right){
      int mid = (left+right) >> 1;
      if (citations[mid] == n-mid){
        return citations[mid];
      }
      else if (citations[mid] < n-mid){
        left = mid+1;
      }
      else
        right = mid-1;
    }
    return n-(right+1);
  }
  public static void main(String[] args){

  }
}