用python写字典树时间会更多，需要将单词排序，长度短的先插入

class tnode(object):
    def __init__(self):
        self.cnt = 0
        self.op = {}

    def insert(self, s):
        flag = True
        cur = self
        for c in s:
            if c not in cur.op:
                cur.op[c] = tnode()
            cur = cur.op[c]
            if cur.cnt == 1:
                flag = False
                break
        cur.cnt = 1
        if cur.op != {}:
            flag = False
        return flag

t = int(input())

for _ in range(t):
    n = int(input())
    rt = tnode()
    a = []
    for _ in range(n):
        a.append(input())
    a = sorted(a)
    flag = True
    for s in a:
        flag = flag and rt.insert(s)
    if flag:
        print('YES')
    else:
        print('NO')