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## 题目内容

Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper, return compute the researcher’s h-index.

According to the definition of h-index on Wikipedia: A scientist has an index h if h of their n papers have at least h citations each, and the other n − h papers have no more than h citations each.

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

Example 1:

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, their h-index is 3.

Example 2:

Input: citations = [1,3,1]

Output: 1

Constraints:

n == citations.length

1 <= n <= 5000

0 <= citations[i] <= 1000

## 方法

有两种方法解题 排序 和 [[计数排序]]

### 排序

时间复杂度和空间复杂度是排序的时间复杂度

1 | class Solution { |

### 计数排序

时间复杂度和空间复杂度都为O(N)

对每个可能的 h 值, 记录对应的论文数量

1 | class Solution { |