h-index.js

/**
 * 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.
 */

/**
 * @param {number[]} citations
 * @return {number}
 */
const hIndex = citations => {
  citations.sort((a, b) => a - b);

  const n = citations.length;
  let max = 0;

  for (let i = 0; i < n; i++) {
    max = Math.max(max, Math.min(citations[i], n - i));
  }

  return max;
};

export { hIndex };