#include<bits/stdc++.h>
using namespace std;
int main(){
    int t;
    cin>>t;
    while(t--){
        long long n,i,j,k,cnt=0,f=0,ans=0;
        cin>>n;
        string a,b,c,d,e,g;
        cin>>a>>b;
        e=a;
        g=b;
        //sort(c.begin(),c.end());
        //sort(d.begin(),d.end());
            for(i=0;i<n-1;i++){
               if(a[i]>a[i+1]){
                  a[i]=b[i];
               }
            }
           // cout<<a<<endl;
    
            if(!is_sorted(a.begin(),a.end())){
                for(i=0;i<n-1;i++){
                    if(b[i]>b[i+1]){
                        b[i]=e[i];
                    }
                }
              //  cout<<b<<endl;
                if(!is_sorted(b.begin(),b.end())){
                    cout<<"No"<<"\n";
                }else{
                    cout<<"Yes"<<"\n";
                }
               
            }else{
               cout<<"Yes"<<"\n";
        }

    }
}