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Saint Louis University

Computer Science 180
Data Structures

Michael Goldwasser

Spring 2012

Dept. of Math & Computer Science


Lab Assignment 07

Topic: Phone List
Source Code: phone.cpp

In-Class Day:

Thursday, 22 March 2012, 10:00am
Submission Deadline: Friday, 23 March 2012, 11:59pm

Techniques:

Use of strings and system sort.

Collaboration Policy

The pre-lab requirement must be completed and submitted individually.

The remainder of the lab activity should be completed working in pairs. One person should submit the result, making sure that both partners' names are clearly identified in that submission.

Please make sure you adhere to the policies on academic integrity in this regard.

Pre-Lab Requirement

Read the complete problem description and then determine what the expected output should be if given the following input:

Prelab input: Prelab output:
3
3
9777039
9772444
3149777039
3
012
12
210
4
3
4
1234
4321


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:

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.

Input: 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.

Output: For each test case, output "YES" if hte list is consistent, or "NO" otherwise.

Example input: Example output:
2
3
911
97625999
91125426
5
113
12340
123440
12345
98346
NO
YES

Hints

Although this problem is about "numbers", you should store all of these as strings.

Then, the key to efficiency for this problem is to first sort the list of strings, and then you can determine consistency by checking whether any entry is a prefix of the one immediately following it.

Useful documentation:


Michael Goldwasser
CSCI 180, Spring 2012
Last modified: Tuesday, 20 March 2012
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