Easy Approach || Simple to understand
Hope you liked it :)\n\n```\nclass Solution {\npublic:\n    void solve(vector &v, int n, int currindex, int &count, int l)\n    {\n        if(currindex >= n)\n 
**Hope you liked it :)**\n\n```\nclass Solution {\npublic:\n    void solve(vector<char> &v, int n, int currindex, int &count, int l)\n    {\n        if(currindex >= n)\n        {\n            count++;\n            return;\n        }\n        for(int i=l; i<v.size(); i++)\n        {\n            solve(v, n, currindex+1, count, i);\n        }\n    }\n    \n    int countVowelStrings(int n)\n    {\n        vector<char> v={\'a\',\'e\',\'i\',\'o\',\'u\'};\n        int count = 0;\n        solve(v, n, 0, count, 0);\n        return count;\n    }\n};
['Backtracking', 'C', 'C++']