#include<cstdio>#include<cstring>#include<cmath>#define LL intstruct Node{ struct Node *br[10]; Node(){ for(LL i=0;i<10;i++) br[i]=NULL; }};Node *head;bool add_tree(char *st){ LL len=strlen(st),k,i,flag,d; Node *s=head; for(k=0;k<len;k++){ d=st[k]-'0'; if(s->br[d]){ s=s->br[d]; if(k==len-1){ return true; } flag=0; for(i=0;i<10;i++) if(s->br[i]){ flag=1; break; } if(!flag) return true; } else{ s->br[d]=new Node; s=s->br[d]; } } return false;}bool del(Node *p){ if(!p) return false; for(LL i=0;i<10;i++){ if(p->br[i]) del(p->br[i]); } delete p; return false;}int main(){ LL t,n,k,flag,i; char st[11]; scanf("%d",&t); while(t--){ head=new Node; for(i=0;i<10;i++) head->br[i]=NULL; flag=0; scanf("%d",&n); while(n--){ scanf("%s",st); k=add_tree(st); if(k) flag=1; } if(flag) puts("NO"); else puts("YES"); del(head); } return 0;}
