1295. Find Numbers with Even Number of Digits

Description

Given an array nums of integers, return how many of them contain an even number of digits.

Example 1:

Input: nums = [12,345,2,6,7896]
Output: 2
Explanation: 
12 contains 2 digits (even number of digits). 
345 contains 3 digits (odd number of digits). 
2 contains 1 digit (odd number of digits). 
6 contains 1 digit (odd number of digits). 
7896 contains 4 digits (even number of digits). 
Therefore only 12 and 7896 contain an even number of digits.

Example 2:

Input: nums = [555,901,482,1771]
Output: 1 
Explanation: 
Only 1771 contains an even number of digits.

Constraints:

1 <= nums.length <= 500
1 <= nums[i] <= 10⁵

Solutions

Solution: Math

Time complexity: O(nlog₁₀(num[i]) -> n)
Space complexity: O(1)

JavaScript

js

/**
 * @param {number[]} nums
 * @return {number}
 */
const findNumbers = function (nums) {
  const isEvenDigitsNumber = num => {
    let digitsNumber = 0;

    while (num) {
      num = Math.floor(num / 10);
      digitsNumber += 1;
    }

    return digitsNumber % 2 === 0;
  };

  return nums.reduce((result, num) => {
    return result + (isEvenDigitsNumber(num) ? 1 : 0);
  }, 0);
};