CountFactors

Count factors of given number n
ℹ️ © Codility, 2009-2018

Problem

A positive integer d is a “factor” of a positive integer n if there exists an integer m such that n = d · m.

For example, 6 is a factor of 24, because m = 4 satisfies the above condition (24 = 6 · 4).

Write a function that, given a positive integer n, returns the number of its factors.

For example, given n = 24, the function should return 8, because 24 has 8 factors, namely 1, 2, 3, 4, 6, 8, 12, 24. There are no other factors of 24.

Assume that:
• n is an integer within the range [1 … 2,147,483,647].

Complexity:
• expected worst-case time complexity is O(sqrt(n));
• expected worst-case space complexity is O(1).

Solution

C#

using System;
class Solution {
  public int solution(int n) {
    int r = 0;
    double t = (double)Math.Sqrt(n);
    int i = 1;
    while (i < t) {
      if (n % i == 0) {
        r += 2;
      }
      i++;
    }
    return r + (i == t ? 1 : 0);
  }
}

Java

import java.lang.Math;
class Solution {
  public int solution(int n) {
    int r = 0;
    double t = (double)Math.sqrt(n);
    int i = 1;
    while (i < t) {
      if (n % i == 0) {
        r += 2;
      }
      i++;
    }
    return r + (i == t ? 1 : 0);
  }
}

JavaScript

function solution(n) {
  let r = 0;
  let t = Math.sqrt(n);
  let i = 1;
  while (i < t) {
    if (n % i == 0) {
      r += 2;
    }
    i++;
  }
  return r + (i == t ? 1 : 0);
}

PHP

function solution($n) {
  $r = 0;
  $t = sqrt($n);
  $i = 1;
  while ($i < $t) {
    if ($n % $i == 0) {
      $r += 2;
    }
    $i++;
  }
  return $r + ($i == $t ? 1 : 0);
}