Happy LadyBugs

//https://www.hackerrank.com/challenges/happy-ladybugs/problem

#include <iostream>

using namespace std;

int main()
{
    int Q,n,res;
    string b;
    cin >> Q;
    for(int a0 = 0; a0 < Q; a0++)
    {
        cin >> n;
        cin >> b;
        res=1;
        for(char i='A'; i<='Z'; i++)
        {
            int cnt=0;
            for(int j=0; j<n; j++)
            {
                if(b[j]==i) cnt++;
            }
            if(cnt==1)
            {
                //if there is only one bug of any kind, it can't be happy 
                //as it cant have any partners.
                res=0; 
                break;   
            }
        }
        if(res)
        {
            int cnt_=0;
            for(int i=0; i<n; i++)
                if(b[i]=='_') cnt_++;
            //if there r no empty cells , we cant't adjust the bugs. But, if they 
            //are already happy we can print yes, so we need to check this condition
            if(cnt_==0)
                for(int i=1; i<(n-1); i++)
                    if(b[i]!=b[i+1] && b[i]!=b[i-1]) 
                    {
                        // not all the bugs are happy.
                        res=0; 
                        break;
                    }
        }
        if(res)
            cout << "YES" << endl;
        else 
            cout << "NO" << endl;
    }
    return 0;
}