1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<stdlib.h>
 6 #include<algorithm>
 7 using namespace std;
 8 const int MAXN=10000+5;
 9 int T,n;
10 struct node
11 {
12     char str[10+5];
13 }a[MAXN];
14 
15 int cmp(const node A,const node B)
16 {
17     return strcmp(A.str,B.str)<0;
18 }
19 
20 int judge(char a[],char b[])
21 {
22     int len=strlen(a);
23     for(int i=0;i<len;i++)
24         if(a[i]!=b[i])
25             return 0;
26     return 1;
27 }
28 int main()
29 {
30     //freopen("in.txt","r",stdin);
31     scanf("%d",&T);
32     while(T--)
33     {
34         scanf("%d",&n);
35         for(int i=0;i<n;i++)
36             scanf("%s",a[i].str);
37 
38         sort(a,a+n,cmp);//利用结构体对字符串排序
39 
40         int ok=0;
41         for(int i=0;i<n-1;i++)
42         {
43             if(judge(a[i].str,a[i+1].str))
44             {
45                 ok=1;
46                 break;
47             }
48         }
49         
50         if(ok)
51             printf("NO\n");
52         else
53             printf("YES\n");
54     }
55     return 0;
56 }