Given a list of phone numbers, determine if it is consistent in the
sense that no number is the prefix of another. Let’s say the phone
catalogue listed these numbers:
• Emergency 911
• Alice 97 625 999
• Bob 91 12 54 26
In this case, it’s not possible to call Bob, because the central would
direct your call to the emergency line as soon as you had dialled the
first three digits of Bob’s phone number. So this list would not be
The first line of input gives a single integer, 1 ≤ t ≤ 40, the number of test cases. Each
test case starts with n, the number of phone numbers, on a separate line, 1 ≤ n ≤ 10000.
Then follows n lines with one unique phone number on each line. A phone number is a
sequence of at most ten digits.
For each test case, output “YES” if the list is consistent, or “NO” otherwise.
本题由旧版NOJ导入，来源：Nordic Collegiate Programming Contest 2007