#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;cin>>t;
while(t--)
{
int n;cin>>n;
string arr;cin>>arr;
int visit[n];
memset(visit,0,sizeof(visit));
int i=0,j=n-1;
int flag=0;
int ans=0;
for(;i<n/2;i++,j--)
{
if(arr[i]==arr[j])continue;
else if(arr[i]==arr[j-1] && visit[j]==0 && visit[j-1]==0)
{
swap(arr[j],arr[j-1]);ans++;
visit[j]=visit[j-1]=1;
}
else if(arr[i+1]==arr[j] && visit[i]==0 && visit[i+1]==0)
{
swap(arr[i],arr[i+1]);ans++;
visit[i]=visit[i+1]=1;
}
else {flag=1;break;}
}
if(flag)cout<<"NO"<<endl;
else {
cout<<"YES"<<endl<<ans<<endl;
}
}
}