README.md

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.

Solutions (Rust)

1. Sort

impl Solution {
    pub fn h_index(citations: Vec<i32>) -> i32 {
        let mut citations = citations;
        citations.sort_unstable_by(|a, b| b.cmp(a));
        let mut h = 0;

        for i in 0..citations.len() {
            h = h.max(citations[i].min(i as i32 + 1));
        }

        h
    }
}

2. Count

impl Solution {
    pub fn h_index(citations: Vec<i32>) -> i32 {
        let mut counter = vec![0; citations.len() + 1];
        for &c in &citations {
            counter[(c as usize).min(citations.len())] += 1;
        }

        let mut s = 0;
        let mut i = counter.len() - 1;
        loop {
            s += counter[i];
            if s >= i {
                return i as i32;
            }
            i -= 1;
        }
    }
}