H-Index II -- LeetCode

Datetime:2016-08-23 01:20:41          Topic: LeetCode           Share

Given an array of citations (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."

For example, given  citations = [3, 0, 6, 1, 5] , which means the researcher has  5 papers in total and each of them had received  3, 0, 6, 1, 5 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, his h-index is  3 .

Note: If there are several possible values for  h , the maximum one is taken as the h-index.

Follow up for  H-Index : What if the  citations array is sorted in ascending order? Could you optimize your algorithm?

思路:二分查找。

注意搜索的边界情况。

 1 class Solution {
 2 public:
 3     int hIndex(vector<int>& citations) {
 4         int left = 0, right = citations.size() - 1;
 5         while (left <= right) {
 6             int mid = left + (right - left) / 2;
 7             if (citations[mid] < citations.size() - mid)
 8                 left = mid + 1;
 9             else if (mid > left && citations[mid - 1] >= citations.size() - (mid - 1))
10                 right = mid - 1;
11             else return citations.size() - mid;
12         }
13         return 0;
14     }
15 };




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