1 /*hdu 1671 ×ÖµäÊ÷*/
 2 #define LOCAL
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<iostream>
 6 using namespace std;
 7 struct Trie
 8 {
 9    struct Trie *next[10];
10    bool tail;
11 };
12 char str[10005][12];
13 void in_Trie(char *s,Trie *root)
14 {
15    Trie *cur=root,*newcur;
16   for(int i=0;s[i]!=‘\0‘;i++)
17   {
18        if(cur->next[s[i]-‘0‘]==NULL)
19      {
20          newcur=new Trie;   //(Trie*)malloc(sizeof(sizeof(Trie)));
21          for(int j=0;j<=9;j++)
22            newcur->next[j]=NULL;
23             newcur->tail=0;
24         cur->next[s[i]-‘0‘]=newcur;
25      }
26     cur=cur->next[s[i]-‘0‘];
27   }
28    cur->tail=1;
29 }
30 bool query(char *s,Trie *root)
31 {
32     int i=0;
33     Trie *cur=root;
34     for(i=0;s[i];i++){
35        if(cur->tail==0&&cur->next[s[i]-‘0‘]!=NULL)
36            cur=cur->next[s[i]-‘0‘];
37       else break;
38     }
39  if(s[i]!=‘\0‘) return 1;
40    return 0;
41 }
42 void dele(Trie *root)
43 {
44   for(int i=0 ; i<=9 ; i++ )
45       if(root->next[i]!=NULL)
46       dele(root->next[i]);
47  // free(root);
48  delete root;
49 }
50 int main()
51 {
52   #ifdef LOCAL
53   freopen("test.in","r",stdin);
54   #endif
55   int t,i,n;
56   Trie *root;
57   scanf("%d",&t);
58   while(t--)
59   {
60        root = new Trie ;
61        for(int j=0;j<=9;j++)
62        root->next[j]=NULL;
63        root->tail=0;
64 
65      scanf("%d",&n);
66     for(i=0;i<n;i++){
67       scanf("%s",str[i]);
68       in_Trie(str[i],root);
69     }
70 
71     for(i=0;i<n;i++)
72       if(query(str[i],root)!=0)
73         break;
74       dele(root);
75       if(i>=n)
76         printf("YES\n");
77       else
78         printf("NO\n");
79   }
80    return 0;
81 }