http://acm.hdu.edu.cn/showproblem.php?pid=1671

题解：字典树

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int ans,cnt,flag,temp;
int a[N][10];
int en[N];
char str[20];
int sum[N];
void insert(char *s){
    int len=strlen(s),p=0;
    for(int i=0;i<len;i++){
        int ch=s[i]-'0';
        if(a[p][ch]==0)a[p][ch]=++cnt;
        p=a[p][ch];
        sum[p]++;
    }
    en[p]=1;
}
bool search(char* s){
    int len=strlen(s),p=0;
    for(int i=0;i<len;i++){
        int ch=s[i]-'0';
        if(a[p][ch]==0)
            return 0;
        p=a[p][ch];
        if(en[p])
            return 1;
    }
    return 1;
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //scanf("%d",&n);
    scanf("%d",&t);
    while(t--){
        memset(a,0,sizeof(a));
        memset(en,false,sizeof(en));
        scanf("%d",&n);
        flag=1;
        cnt=0;
        for(int i=1;i<=n;i++){
            scanf("%s",str);
            if(search(str))//printf("OO\n");
                flag=0;
            insert(str);
        }
        if(flag)
            printf("YES\n");
        else
            printf("NO\n");
    }


    //cout << "Hello world!" << endl;
    return 0;
}