274. H-Index

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:

```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.

274. H-Index
``````struct Solution;

impl Solution {
fn h_index(citations: Vec<i32>) -> i32 {
let n = citations.len();
let mut count: Vec<usize> = vec![0; n + 1];
for c in citations {
let i = c as usize;
if i < n {
count[i] += 1;
} else {
count[n] += 1;
}
}
let mut h = n;
let mut sum = 0;
while sum <= h {
sum += count[h];
if sum >= h {
return h as i32;
}
h -= 1;
}
0
}
}

#[test]
fn test() {
let citations = vec![3, 0, 6, 1, 5];
let res = 3;
assert_eq!(Solution::h_index(citations), res);
}
``````