#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define PI acos(-1.0)
#define vi vector<ll>
#define pii pair<ll,ll>
#define vii vector<pii>
#define rsrt(a) sort(a.rbegin(),a.rend())
#define srt(a) sort(a.begin(),a.end())
#define rev_str(str) reverse(str.begin(),str.end());
#define print(v) for(auto i:v) cout<<i<<" ";cout<<endl;
#define fast ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define rep(i,a,b) for(ll i =a ;i<b;i++)
#define per(i,b,a) for(ll i=b;i>=a;i--)
bool sortByValue(const pair<int,int>& a,const pair<int,int>& b){
    return a.second > b.second;
}

void solve(){
    ll n;cin>>n;
    string a,b;cin>>a>>b;
    string s,k;
    s = a;
    k = b;
    rep(i,0,n-1){
        if(s[i]>s[i+1]){
            if(k[i]<=s[i+1]){
                swap(k[i],s[i]);
                continue;

            }
            if(k[i+1]>=s[i]){
                swap(s[i+1],k[i+1]);continue;
            }
        }
    }
    rep(i,0,n-1){
        if(b[i]>b[i+1]){
            if(a[i]<=b[i+1]){
                swap(a[i],b[i]);
                continue;

            }
            if(a[i+1]>=b[i]){
                swap(b[i+1],a[i+1]);continue;
            }
        }
    }
    if(is_sorted(s.begin(),s.end()) || is_sorted(b.begin(),b.end()) ){
        cout<<"Yes"<<endl;
    }
    else{
        cout<<"No"<<endl;
    }
}
int main(){
    fast;
    ll t=1;cin>>t;
    while(t--){
        solve();
    }
    return 0;
}