sort가 핵심!
import java.util.Arrays;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int T = sc.nextInt();
for(int i=0; i<T; i++) {
int N = sc.nextInt();
String[] arr = new String[N];
int cnt=0;
for(int j=0; j<N; j++) {
arr[j] = sc.next();
}
Arrays.sort(arr);
for(int j=0; j<N-1; j++) {
if(arr[j+1].startsWith(arr[j])) {
cnt++;
break;
}
}
if(cnt==0)
System.out.println("YES");
else
System.out.println("NO");
}
}
}