#1704 - Determine if String Halves Are Alike

Easy • View on LeetCode • View on GitHub

Problem Description

You are given a string s of even length. Split this string into two halves of equal lengths, and let a be the first half and b be the second half.

Two strings are alike if they have the same number of vowels ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'). Notice that s contains uppercase and lowercase letters.

Return true if a and b are alike. Otherwise, return false.

Solution

/**
 * @param {string} s
 * @return {boolean}
 */
var halvesAreAlike = function(s) {
  const vowels = new Set(['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']);
  let firstHalfVowels = 0;
  let secondHalfVowels = 0;
  const mid = s.length / 2;

  for (let i = 0; i < mid; i++) {
    if (vowels.has(s[i])) firstHalfVowels++;
    if (vowels.has(s[i + mid])) secondHalfVowels++;
  }

  return firstHalfVowels === secondHalfVowels;
};