Clean Code || c++ || easy to understand!
\nclass Solution {\npublic:\n    long long countVowels(string word) {\n        vector<char> f = {\'a\',\'e\',\'i\',\'o\',\'u\'};\n        set<char> s;\n        
```\nclass Solution {\npublic:\n    long long countVowels(string word) {\n        vector<char> f = {\'a\',\'e\',\'i\',\'o\',\'u\'};\n        set<char> s;\n        s.insert(f.begin(),f.end());\n        long long n = word.length();\n        long long sum =0;\n        for(long long i=0; i<n; i++)\n        {\n            if(s.find(word[i])!=s.end())\n            {\n                sum += (i+1)*(n-i);\n            }\n        }\n        return long(sum);\n    }\n};\n```
['Math', 'C']