LeetCode 274: H-Index

274. H-Index

Difficulty: Medium

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.

思路

本题题意：找到一个数字h，使得数组中至少有h个元素的值大于等于h，其余元素的值不超过h。

首先对数组进行排序，降序排列元素，这时，h需要满足的条件可描述为：数组的前h个元素大于等于h。

元素的序号加1表示数组中有几个元素大于等于该元素，一旦元素值不大于元素序号，h则为该元素序号。

代码

[C++]

class Solution {
public:
int hIndex(vector<int>& citations) {
if(citations.size() < 1)
return 0;
sort(citations.begin(), citations.end(), greater<int>());
int h = 0;
while (h < citations.size() && citations[h] > h)
++h;
return h;
}
};