**Title: **H-Index **Source: **leetcode.com

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.

- An easy approach is to sort the array first.
- What are the possible values of h-index?
- A faster approach is to use extra space.

### Python solution

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''' https://leetcode.com/problems/h-index/ ''' class Solution(object): def hIndex(self, citations): """ :type citations: List[int] :rtype: int """ if not citations: return 0 citations.sort(reverse=True) ln = len(citations) h = 0 i = 0 for i in range(1,ln): if citations[i] < citations[i-1]: if (h < i <= citations[i-1]): h = i elif citations[i] == i: h = i if (citations[i] >= h) : if citations[i] > i: h = i+1 else: h = citations[i] return h |