#1390 - Four Divisors

Medium • View on LeetCode • View on GitHub

Problem Description

Given an integer array nums, return the sum of divisors of the integers in that array that have exactly four divisors. If there is no such integer in the array, return 0.

Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var sumFourDivisors = function(nums) {
  function countDivisors(num) {
    const divisors = new Set();
    for (let i = 1; i * i <= num; i++) {
      if (num % i === 0) {
        divisors.add(i);
        divisors.add(num / i);
      }
    }
    return divisors;
  }

  let result = 0;
  for (const num of nums) {
    const divisors = countDivisors(num);
    if (divisors.size === 4) {
      const sum = [...divisors].reduce((acc, val) => acc + val, 0);
      result += sum;
    }
  }

  return result;
};