Phone List

#include <bits/stdc++.h>
using namespace std;

const int SIZE = 1e5 + 10;
int trie[SIZE][10], sign[SIZE], tot = 1;
char ss[SIZE][20];

void insert(char* str) {
	int len = strlen(str), p = 1;
	for (int i = 0; i < len; ++i) {
		int ch = str[i] - '0';
		if (!trie[p][ch]) trie[p][ch] = ++tot;
		p = trie[p][ch];
	}
	sign[p]++;
}

bool search(char* str) {
	int len = strlen(str), p = 1;
	for(int i = 0; i < len; ++i) {
		int ch = str[i] - '0';
		if (sign[p]) return true;
		p = trie[p][ch];
	}
	return false;
}

bool solve(int n) {
	for (int i = 1; i <= n; ++i) insert(ss[i]);
	for (int i = 1; i <= n; ++i) {
		if (search(ss[i])) return true;
	}
	return false;
}

int main() {
	int T; cin >> T;
	while (T--) {
		int n; cin >> n;
		for (int i = 1; i <= n; ++i) scanf("%s",ss[i]);
		if (solve(n)) puts("NO");
		else  puts("YES");
		memset(trie,0,sizeof(trie));
		memset(sign,false,sizeof(sign));
		tot = 1;
	}
	return 0;
}