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Find Loveable strings containing permutations of ANU


Anubhav has a crush on Anu. Therefore he likes the letters A,N and U the most.

He likes those strings which consists of only A N U

According to him, the strings containing A,N and U only are "LOVABLE" If they contain either of these patterns:


1) ANU


2) AUN


3) NAU


4) NUA


5) UAN


6) UNA


He asks you to find out how many LOVABLE strings are there of length N.


Note: Assume all strings are made of A,N,U. Consider all other alphabets as non-existent.


Input format: First line contains T the number of test cases. Next T lines contain a single integer N, denoting the length of string


Output format: Output the count of LOVABLE strings of length N in a single line for each test case


Constraints:


1<= T <= 30


1<= N <= 30

Solution : 

// Online C++ compiler to run C++ program online
#include<bits/stdc++.h>
using namespace std;
class Solution{
   
    int a = 1;
    int n1 = 7;
    int u = 3;
    public :
    int solve(int n , int pre , int pre_pre , int sum , bool x  )
    {  
        if(n ==0)
        {
            if(x)
            return 1;
            return 0;
        }
        long long result =0;
        if(sum == a + pre + pre_pre )
        {
            result += solve(n-1 , a , pre , sum , true );
        }
        else
        result += solve(n-1 , a , pre , sum , x);
       
        if(sum == n1 + pre + pre_pre )
        {
            result += solve(n-1 , n1 , pre , sum , true );
        }
        else
        result += solve(n-1 , n1 , pre , sum , x);
       
        if(sum == u + pre + pre_pre )
        {
            result += solve(n-1 , u , pre , sum , true );
        }
        else
        result += solve(n-1 , u , pre , sum , x);
       
        return result;
       
       
       
       
    }
    int Loveable(int  n )
    {
        if(n == 0 || n==1 || n==2)
        {
            return 0;
        }
        return solve(n , -1 , -1 , 11 , false);
       
       
    }
};


int main() {
   
    Solution s ;
    int n = 4;
    int x = s.Loveable(n);
    cout << x << " "<<"\n";
}


The dynamic programming solution will be uploaded soon, Stay tuned.

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