README.md

275. H-Index II

Given an array of citations sorted in ascending order (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 = [0,1,3,5,6]
Output: 3
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had 
             received 0, 1, 3, 5, 6 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.

Follow up:

• This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
• Could you solve it in logarithmic time complexity?

Solutions (Rust)

1. Binary Search

impl Solution {
    pub fn h_index(citations: Vec<i32>) -> i32 {
        let len = citations.len();
        let mut l = 0;
        let mut r = len;
        let mut ret = 0;

        while l < r {
            let m = (l + r) / 2;

            if citations[m] as usize <= len - m {
                ret = ret.max(citations[m]);
                l = m + 1;
            } else {
                ret = ret.max((len - m) as i32);
                r = m;
            }
        }

        ret
    }
}