## Question

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.

**Hint:**

- 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.

## Solution

**Result:** Accepted **Time:** 4 ms

Here should be some explanations.

```
class Solution {
public:
int hIndex(vector<int>& cit) {
if(cit.size() < 1) return 0;
sort(cit.begin(),cit.end());
reverse(cit.begin(),cit.end());
int i;
for( i = 0; i < cit.size() && cit[i] > i; i++);
return i;
}
};
```

**Complexity Analytics**

- Time Complexity:
- Space Complexity: