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Saint Louis University

Computer Science 2100
Data Structures

Michael Goldwasser

Fall 2015

Dept. of Math & Computer Science


Lab Assignment 05

Topic: Symmetric Order (again)
Source Code: order.cpp
Live Archive Ref#: 3055

Pre-lab Due:

Thursday, 15 October 2015, 10:00am
Submission Deadline: Friday, 16 October 2015, 11:59pm

Techniques:

Use of a vector.

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:
4
Bob
Bill
Betty
Bobby
5
Ed
Eddie
Eliza
Edward
Elizabeth
0


Symmetric Order

In your job at Albatross Circus Management (yes, it's run by a bunch of clowns), you have just finished writing a program whose output is a list of names in nondescending order by length (so that each name is at least as long as the one preceding it). However, your boss does not like the way the output looks, and instead wants the output to appear more symmetric, with the shorter strings at the top and bottom and the longer strings in the middle. His rule is that each pair of names belongs on opposite ends of the list, and the first name in the pair is always in the top part of the list. In the first example set below, Bo and Pat are the first pair, Jean and Kevin the second pair, etc.

Input: The input consists of one or more sets of strings, followed by a final line containing only the value 0. Each set starts with a line containing an integer, n, which is the number of strings in the set, followed by n strings, one per line, sorted in nondescending order by length. None of the strings contain spaces. There is at least one and no more than 15 strings per set.  Each string is at most 25 characters long. 

Output: For each input set print "SET n" on a line, where n starts at 1, followed by the output set as shown in the sample output.

Example input: Example output:
7
Bo
Pat
Jean
Kevin
Claude
William
Marybeth
6
Jim
Ben
Zoe
Joey
Frederick
Annabelle
5
John
Bill
Fran
Stan
Cece
0
SET 1
Bo
Jean
Claude
Marybeth
William
Kevin
Pat
SET 2
Jim
Zoe
Frederick
Annabelle
Joey
Ben
SET 3
John
Fran
Cece
Stan
Bill

Hints

This is a simple problem. Our reason for using it is specifically so that you can get some practice using the std::vector class that is included in the <vector> C++ library. Although I realize that you could preallocate a fixed-sized array, I ask that you use the vector class to implementing your solution. If you need a reminder, you can find online documentation regarding its usage. But its essentially an array that resizes as you push things to the back

Start by reading all the strings into a vector, using the given order. Then, to get the output in the desired order, write one loop to print out all elements of the vector that have even index (i.e., v[0], v[2], v[4], ...). Then write a second loop that starts at the end moving backward while printing all items that have an odd index (i.e., v[5], v[3], v[1]). The only care needed is to ensure that your loops execute the correct number of iterations.


Michael Goldwasser
CSCI 2100, Fall 2015
Last modified: Tuesday, 13 October 2015
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