Count Vowels in a String

function countVowels(s) {
  let count = 0;
  for (let ch of s.toLowerCase()) {
    if ('aeiou'.includes(ch)) count++;
  }
  return count;
}
                  

Explanation: We iterate through each character and increment the count if it is a vowel.

⏱ O(n) | 💾 O(1)

class Solution {
  public int countVowels(String s) {
    int count = 0;
    for (char c : s.toLowerCase().toCharArray()) {
      if ("aeiou".indexOf(c) != -1) count++;
    }
    return count;
  }
}
                  

Explanation: Each character is checked against a vowel set.

⏱ O(n) | 💾 O(1)

def count_vowels(s):
    return sum(1 for c in s.lower() if c in 'aeiou')
                  

Explanation: We count characters that belong to the vowel set.

⏱ O(n) | 💾 O(1)