#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() + min(s[0], p[0]);
    
    for (int i = 1; i < n; i++) {
        if (min(s[i], p[i]) >= ans[i - 1]) {
            ans += string() + min(s[i], p[i]);
        }
        else {
            ans += string() + max(s[i], p[i]);
        }
    }

    if (is_sorted(ans.begin(), ans.end())) {
        cout << "Yes\n";
    }
    else {
        cout << "No\n";
    }

    // cout << s << " " << p << endl;






}

int main() 
{

    ios::sync_with_stdio(false); cin.tie(0);
    //ll t = 1;
    ll t; cin >> t;
    while(t--) {
        solve();
    }


}