Code : Valid Word

class Solution {
  public:
    bool isValid(string word);
};

bool Solution::isValid(string word) {
    int n = word.size();
    if (n < 3) {
        return false;
    }

    vector<char> is_vowel(26, false);
    vector<char> vowels_list = {'a', 'e', 'i', 'o', 'u'};
    for (int i = 0; i < vowels_list.size(); i++) {
        is_vowel[vowels_list[i] - 'a'] = true;
    }

    bool vowel_found = false, consonant_found = false;
    for (int i = 0; i < n; i++) {
        char ch = word[i];
        ch = tolower(ch);
        if (ch >= '0' && ch <= '9') {

        } else if (ch >= 'a' && ch <= 'z') {
            if (is_vowel[ch - 'a']) {
                vowel_found = true;
            } else {
                consonant_found = true;
            }
        } else {
            return false;
        }
    }

    if (vowel_found && consonant_found) {
        return true;
    }
    return false;
}