leetcode-274-H-Index

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描述

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.”

Example:

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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.

分析

这题要求我们求H指数，思路不复杂，将某人发表的所有 SCI 论文按照引用次数从高到低排序，从高到低编号为 0，1，2 … n，当 n >= 引用数时，这个值就是某人的 H 指数。这个指数可以用来评估研究人员的学术产出数量和学术产出水平。

解决方案1(Java)

在 Java 中，自定义 int 类型的 compare 方法还得先把 int 转换成 Integer，见 https://stackoverflow.com/questions/7414299/sorting-int-array-in-descending-order ，索性用从低到高的顺序，只要序号对了就行。如果用 Python 就直观多了。

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class Solution {
    public int hIndex(int[] citations) {
        Arrays.sort(citations);
        
        int length = citations.length;
        for (int i = length-1; i >= 0; i--) {
            if (length-i-1 >= citations[i]) {
                return length-i-1;
            }
        }
        return citations.length;
    }
}

解决方案2(Python)

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class Solution:
    def hIndex(self, citations):
        """
        :type citations: List[int]
        :rtype: int
        """
        for i, v in enumerate(sorted(citations, reverse=True)):
            if i >= v:
                return i;
        return len(citations);

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