Program 3
Due: April 2, 2009

Write a program that maintains certain data about airlines. It contains
two kinds of data for each airline:
1. The name of the airline: a string which may contain blanks

2. Sets of airports that a passenger can travel among using only this
   airline.  That is, for any two airports that belong to the same set, a
   passenger can travel from one to the other (possibly using some other
   airports in the same set).  These sets are therefore a
   partitioning of the set of the airports that the airline can fly into
   and out of.  Note that a set containing only one airport is possible.
   It would be an airport where the airline may eventually be able to fly
   into and out of, but at the moment, it has no flights to or from it.

Each airport has the following data:
  code: a three letter code that uniquely identifies the airport
  name: a string that could contain blanks
 
This data can be updated with the following commands.  Each command has a two
letter abbreviation (upper or lower case), which is indicated in
parentheses after its name.  Some commands also have arguments shown in angle
brackets (<>).

1. Add Airport (AA) "<airline name>" <airport code>

   If there is no airline with that name, then a new airline with that name is
   created.  If there is no airport with that code, then a new airport with that code
   is created, and the program prompts the user for the name of the new airport.
   If the airline already exists and the airport is already a member of one of
   the sets belonging to the airline, then an error has occured.  If the airport
   is not yet a member of one of the sets belonging to the airline, then it
   becomes the only member of a new set belonging to the airline.
      
2. Add Connection (AC) "<airline name>" <code1> <code2>

   If <code1> and <code2> are valid airport codes that are members of different
   sets of the airline, then a new set is formed consisting of the union of the two
   sets, and the two old sets are removed. If the airports are already members of
   the same set, then a message to that effect should be generated.

3. List Airlines (LA)

   Displays all airlines and their airports, indicating which airports belong to
   the same set.  How you do this is up to you, but it should be clear.

4. Check Connection (CC) <airline> <code1> <code2>

   If <code1> and <code2> are valid airport codes, then the program checks
   whether they are members of the same set belonging to the airline. If they are,
   then it outputs a message saying so.  If there are no connections, then it should
   say so.

5. Quit (Q)

   The program ends.

Here's an example (user responses are shown in red):

Please enter a command:  aa  "USAir" ord
Airport's name = Orlando
Please enter a command:  aa  "USAir" lax
Airport's name = Los Angeles
Please enter a command:  aa  "USAir" lag
Airport's name = La Guardia
Please enter a command:  ac "USAir" lax lag

Connection added between lax (Los Angeles) and
lag (La Guardia).

Please enter a command:  la

          LIST OF AIRLINES

Airports for USAir

CODE  NAME                 BELONGS TO
lag   La Guardia               Set 2
lax   Los Angeles              Set 2
ord   Orlando                  Set 1

Please enter a command:  cc "USAir" lax ord

There are no connections between lax (Los Angeles)
and ord (Orlando).

Please enter a command:  ac "USAir" lag     ord

Connection added between lag (La Guardia) and
ord (Orlando).

Please enter a command:  cc "USAir" lax ord

There are connections between lax (Los Angeles)
and ord (Orlando)

Please enter a command:q

Use the command and data prompts as shown above. You don't have to use the same formats for the outputs of commands like la or cc; in fact, you should be able to do better.

1. Your program must use a general tree class similar to the UNION/FIND Gentree class shown in Fig. 6.4 of the text. You may want to add other functions, and you can make FIND a public function if you like.
2. The general tree class should use the parent pointer implementation similar to Fig. 6.4, but with the weighted union rule and path compression. You can base your design on code from the textbook's website, or do it from scratch.

Turn in:

1. Hardcopy of all your source code.
2. Hardcopy of your program's execution. It should show all prompts and output from the program, including error messages, and all commands and data entered by the user.
3. Submit your source code files and an executable file named p3 by copying (or ftping) them to a specially designated directory in AFS. Each person in the class has a subdirectory which has the same name as your login name in /afs/cu/class/cs344jl

   Within this individual directory, create a subdirectory named p3. Copy all your source files and the executable file p3 into your p3 directory, including header files, but no object files. So, for example, if your login name was smithjd then your files should be copied to /afs/cu/class/cs344jl/smithjd/p3. These directories have permissions set so that no one other than yourself and Prof. Lynch can read the files. You may, of course, use whatever operating system and compiler you wish to develop your code, but the version you turn in, both hardcopy and the files submitted to AFS, must compile with g++ and run under polaris. Note: you can't compile and run your program in your /afs/cu/class/cs344jl/... directory. You can do it in your own polaris directory and then transfer the files to /afs/...

• Proper implementation of all classes that the program uses, in particular, the class that implements UNION/FIND. Follow the directions above. If you are using code that you did not create, identify where it came from, and clearly identify and explain with comments any changes that you made to it.
• Correctness of execution. The test run should demonstrate this.
• Error checking. There are many possible errors a user of this program can make, and they are not explicitly mentioned above. You need to figure out what the possible errors are. Make sure that your program handles them gracefully, and that your test run includes examples of the errors that can occur.
• Readability of the code: commented and well-structured, so that it is clear what the algorithms and data structures are doing. Use an accepted C++ style. The style of the text is fine, or you can use whatever style you learned in previous courses. Whatever you do, be consistent. Also, the comments should describe all ADTs that are used.
• Appearance of the output. In particular, the output of the LA and CC commands should be neat and easy to read.
• Timely submission of your program. All hardcopy must be turned in on the due date. You can turn it in to me until 3:00PM on the due date. Late programs will not be accepted. Printouts submitted electronically will be ignored.