H index ii

Array Binary Search

39.4% acceptance

Jan 12, 2026

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162

Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper and citations is sorted in non-descending order, return the researcher's h-index. According to the definition of h-index on Wikipedia: The h-index is defined as the maximum value of h such that the given researcher has published at least h papers that have each been cited at least h times. You must write an algorithm that runs in logarithmic time.

Solution

Rust

Time O(n log n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn h_index_ii(citations: Vec<i32>) -> i32 {
    let n = citations.len();
    let mut left = 0;
    let mut right = n;
    
    while left < right {
      let mid = left + (right - left) / 2;
      if citations[mid] >= (n - mid) as i32 {
        right = mid;
      } else {
        left = mid + 1;
      }
    }
    
    (n - left) as i32
  }
}