Not able to solve

#1

Hii…
I was giving the leetcode challenge… which has just finished.
This is the 2nd question…


I was not able to come with proper solution… Some logic realted to recursion came to my mind…
Please see this question.
Thanks

#2

Yes a simple solution to this is by recursion:

class Solution {
    
    int count = 0;
   void helper(int sIndex, int n)
    {
        if(n ==0) 
        {
            count++;
            return;
        }
        
        for(int i =sIndex; i<5; i++)
        {
            helper(i,n-1);
        }        
    }
public:
    int countVowelStrings(int n) {
        helper(0,n);
        return count;
    }
};

If you work with some test cases, you may observe that there is a pattern being followed. I would suggest you to go through this O(n) approach .