#275 - H-Index II

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Problem Description

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 ascending 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

/**
 * @param {number[]} citations
 * @return {number}
 */
var hIndex = function(citations) {
  let start = 0;

  for (let end = citations.length - 1; start <= end;) {
    const middle = Math.floor((start + end) / 2);
    if (citations.length - middle - 1 < citations[middle]) {
      end = middle - 1;
    } else {
      start = middle + 1;
    }
  }

  return citations.length - start;
};