java backtrack solution very simple
\n int ans;\n    public int countVowelStrings(int n) {\n       // char[] ch ={\'a\',\'e\',\'i\',\'o\',\'u\'};\n        ans=0;\n        count(0,n);\n        retu
```\n int ans;\n    public int countVowelStrings(int n) {\n       // char[] ch ={\'a\',\'e\',\'i\',\'o\',\'u\'};\n        ans=0;\n        count(0,n);\n        return ans;\n    }\n    void count(int src,int n){\n        if(n==0){ans++;return;}\n        for(int i=src;i<5;i++){\n            count(i,n-1);\n        }\n    }\n```
['Backtracking', 'Java']