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

Input: citations = [3,0,6,1,5]
Output: 3 
Explanation: [3,0,6,1,5] 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, her h-index is 3.
 

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

Solution:

Python

class Solution:
    def hIndex(self, citations):
        """
        :type citations: List[int]
        :rtype: int
        """
        h = 0
        citations.sort(reverse = True)
        for i in range(len(citations)):
            if citations[i]>h:
                h += 1
        return h  
 

解題思路： 本題其實很簡單，這個題目抽象出來就是在陣列中找到h個大於h的數（這裡我覺得是有歧義的，英文中先說at least h citations each，也就是包含h，而後面又說 no more then ,從結果來判斷，應該是h個大於h的數），剩下的數都不大於h。這裡的h應該從0開始，我們先將陣列進行降序排列，依次將陣列中的數和h進行比較，當陣列中的數大於h的時候，h就加一，然後再與陣列的下一個數進行比較，直到陣列遍歷完成，返回h即可。