UVa Q11362

#include <bits/stdc++.h>
using namespace std;

string s[10000];

int32_t main(){
    int t;
    cin >> t;
    while(t--){
        int n;
        cin >> n;
        for(int i = 0; i < n; ++i)cin >> s[i];
        sort(s, s+n);
        bool yes = 1;
        for(int i = 1; i < n && yes; ++i){//s[i], s[i-1]
            if(s[i].size() < s[i-1].size())continue;
            bool no = 1;
            for(unsigned j = 0; j < s[i-1].size() && no; ++j){
                if(s[i-1][j] != s[i][j])no = 0;
            }
            if(no)yes = 0;
        }
        if(yes)cout << "YES\n";
        else cout << "NO\n";
    }
    return 0;
}