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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aronzx: 2017-09-01 08:09:44

My first Trie !

Arka Roy: 2017-08-17 13:42:05

don't feel satisfied with AC through sort !! go for tries :)

mddaud001: 2017-08-10 22:37:02

My First Trie . Feeling Blessed

rohit9934: 2017-07-02 19:47:07

Weak test cases. sorting solution must not pass.

iammangod96: 2017-06-13 13:44:53

First ever TRIE problem solved. No solutions seen, no excuses, only pure love :)

leafbebop: 2017-06-05 17:01:16

why even sort when a prime=150003 and a hash table can get the way.

aexpo: 2017-05-30 19:46:38

1.Take care while sorting! Don't just directly use inbuilt sort function over strings.
2.Sort according to length of string(that would be helpful)
3.There can be a '0' at the start of a number. Thus if you are avoiding tries and using sorting pay attention to the 0 at the start. eg. 012 is not a prefix of 12345.
No need to pay attention to above points if you are using tries.

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

Added by:Andres Galvis
Time limit:1s
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