PHONELST - Phone List

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Phone List

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 consistent.


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.




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prabodh prakash: 2017-05-01 09:18:21

I found python to be too slow for this problem. Solved using ditto algorithm in cpp. Got a WA due to a wild character being printed in output :|

Last edit: 2017-05-01 10:28:03
ANKIT JAIN: 2017-04-10 21:17:46

My first try using trie :) Nice questions !! loved it !!

aditya9125: 2017-03-28 19:23:39

Prefer "Trie".Checking can be done at the time of insertion.

Last edit: 2017-03-28 19:24:12
sonali9696: 2017-03-23 07:42:08

Note the difference between sorting of numbers and lexigraphically sorting the numbers taken as string :)

epsilonalpha: 2017-03-14 18:30:42

First solved via sorting, then via Tries. First problem on tries!

da_201501181: 2017-03-06 16:33:13

Solved using sorting..!! Will be back with Trie..!!

scorpion_ajay: 2017-02-28 22:31:13

prefer using TRIE over sort function.....otherwise no use ;)
Got several WA's for silly mistake.... finally AC.... first TRIE on spoj :P

cake_is_a_lie: 2017-02-15 16:59:27

Got 4 SIGFPEs for it (because I'm silly and can't do simple math), but the 0.01s was worth it. Could probably get 0.00s but I'm too lazy to write my own sort function.

saurav786: 2016-12-22 18:19:29

NO need of trie, sort the string of array lexigraphically and do a pairwise checking from top :-D

rajeev_899: 2016-11-27 08:27:59

AC in one go

Added by:Andres Galvis
Time limit:0.177s-0.532s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO NODEJS PERL6 VB.NET
Resource:Nordic Collegiate Programming Contest 2007