#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define nline cout<<"\n"
#define fast ios_base::sync_with_stdio(false),cin.tie(0)
#define ain(A, B, C) assert(IN(A, B, C))
#define ull unsigned long long int
#define ll long long int
#define pii pair<int,int>
#define MAXX 100009
#define fr(a,b,i) for(int i=a;i<b;i++)
vector<int>G[MAXX];
struct node
{
bool leaf;
struct node* child[10];
node()
{
for(int i=0;i<10;i++)child[i]=NULL;
leaf=false;
}
};
struct node* root;
bool add(string &s)
{
struct node* curr=root;
for(int i=0;i<s.length();i++)
{
int SS=s[i]-'0';
if(curr->child[SS]==NULL)
curr->child[SS]=new node();
curr=curr->child[SS];
}
for(int i=0;i<10;i++)
{
if(curr->child[i]!=NULL)
return true;
}
curr->leaf=true;
return false;
}
void deleteme(node* curr)
{
for(int i=0;i<10;i++)
if(curr->child[i])
deleteme(curr->child[i]);
delete curr;
}
int main()
{
fast;
int t;
cin>>t;
while(t--)
{
root=new node();
int n,f=0;
cin>>n;
for(int i=0;i<n;i++)
{
string s;
cin>>s;
if(add(s)){f=1;}
}
if(f)
cout<<"NO"<<endl;
else
cout<<"YES"<<endl;
deleteme(root);
}
return 0;
}
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