Lab Assignment 05

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:

Tanning Salon

Tan Your Hide, Inc., owns several coin-operated tanning salons. Research has shown that if a customer arrives and there are no beds available, the customer will turn around and leave, thus costing the company a sale. Your task is to write a program that tells the company how many customers left without tanning.

The input consists of data for one or more salons, followed by a line containing the number 0 that signals the end of the input. Data for each salon is a single line containing a positive integer, representing the number of tanning beds in the salon, followed by a space, followed by a sequence of uppercase letters. Letters in the sequence occur in pairs. The first occurrence indicates the arrival of a customer, the second indicates the departure of that same customer. No letter will occur in more than one pair. Customers who leave without tanning always depart before customers who are currently tanning. There are at most 20 beds per salon.

For each salon, output a sentence telling how many customers, if any, walked away. Use the exact format shown below.

2 ABBAJJKZKZ
3 GACCBDDBAGEE
3 GACCBGDDBAEE
1 ABCBCA
0

All customers tanned successfully.
1 customer(s) walked away.
All customers tanned successfully.
2 customer(s) walked away.

Hints

I'll admit that I picked this problem because, superficially, it seemed like the salon behaves sort of like a stack, or a queue, or a leaky stack, or something along those lines. In reality, none of those abstractions apply.

My recommendation for data structures is the following:

• bool tanning[26]
  An array that notes who is currently in a bed, with tanning[0] set to true if A is tanning, tanning[1] true if B is tanning, and so on.

  We will rely on the fact that people are represented by the upper case letters from A to Z and that we can convert those characters to indices from 0 to 25. Given character value val the appropriate index is computed as val - 'A'.

• bool known[26]
  Although not entirely necessary, it will be helpful to keep track of whether you have seen a particular alphabet symbol in the input (to more easily distinguish between whether a customer is arriving or departing). Such an array could be used for this purpose, again using the mapping from characters A to Z into indicies 0 to 25.

• int numTanning
  A count of how many people are currently tanning (i.e., how many beds are full). Admittedly, we could write a loop to count how many values are set to true in the previous array, but why not make it even easier.

• int numMisses
  Count how many times you see a customer at a time when all the beds are full. The only catch is that such a customer has two characters in the input sequence, one for when they arrive and one for when they leave. For now, think of each independently, thereby marking two misses per such a customer. You can always make the proper adjustment before outputting the real answer.

Judge's Data

You can run the automated judge's tests on turing to test the correctness of your program (although you must still formally submit the source code via the course website). If you are working on your own machine (or if you just want to examine the judge's inputs and expected outputs), we provide them here.