#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'

void solve() 
{
    ll n; cin>>n;
    string s,p; cin>>s>>p;

    string ans = "";
    string ans2= "";
    ans+=s[0];
    for(ll i=1; i<n; i++)
    {
        if(s[i-1]<=s[i] && p[i]>=s[i-1] && s[i]<=p[i]){
            ans += p[i];
        }
        else if(s[i-1]>s[i]&& p[i]>=s[i-1] && s[i]<p[i]) ans+= p[i];
        else ans += s[i];

    }
    ans2+=p[0];
    for(ll i=1; i<n; i++)
    {
        if(p[i-1]<=p[i] && s[i]>=p[i-1] && p[i]<=s[i]){
            ans2 += s[i];
        }
        else if(p[i-1]>p[i]&& s[i]>=p[i-1] && p[i]<s[i]) ans2+= s[i];
        else ans2 += p[i];

    }
   
    int ok = 1, ok2 = 1;
    for(ll i=1; i<n; i++)
    {
        if(ans[i]<ans[i-1])ok = 0;
        if(ans2[i]<ans2[i-1]) ok2 = 0;
    }
    if(ok || ok2) cout<<"Yes"<<endl;
    else cout<<"No"<<endl;
    


}

int main() 
{

    ios::sync_with_stdio(false); cin.tie(0);
    ll t; cin >> t;
    while(t--) {
        solve();
    }


}