CPSC 221 Programming Project 1: Queues, Simulation of an Airport Runway


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Part 1: Add Two New Functions to the LQueue Class
In Part 1, you will use the LQueue class, header file, and driver (main function). You are provided
with a set of sample code and a Makefile, and you should verify that you can compile, link, and
execute the code successfully. You will be adding two new member functions to the LQueue class:
(1) A function to search through a queue for a particular key value, and if found, move the node to
the front of the same queue. Call the void function move_to_front with an appropriate input
● This function might be useful in an airport situation where an emergency requires a plane
to get landing priority (while other planes circle/wait); or, where a plane moves to the front
of the queue for prioritized take-off.
(2) A function that takes two queues that are each ordered according to a given field (so be sure to
include a sequence number, time, or some other measure in the data portion of a node), and merges
the two queues into one queue whose absolute order of the merged elements is kept. For example,
if queue 1 has nodes with sequence numbers of 7, 10, and 15; and if queue 2 has nodes with
sequence numbers 1, 2, 7, 16, 17—then the result should be a single queue with order 1, 2, 7, 7
(arbitrarily break ties), 10, 15, 16, and 17. Call the function merge_two_queues with appropriate
parameter(s). A recommended function call is: q1.merge_two_queues(q2) where queues 1 and
2 already exist. After the merge operation, queue 1 should have all the elements, and queue 2
should be empty. Note that the nodes were originally dynamically allocated, so it is OK to move
them around without fearing that they’ll be lost—providing you don’t delete their storage or lose
their addresses.
● This function might be useful in an airport with multiple runways, where one of the
runways is temporarily shut down due to an emergency, bad weather, maintenance, etc.
Adequately test your new functions. You’ll need to change the driver to convince yourself and the
marker that your two functions work.
Part 2: Simulating Airport Runway Activity using Landing and Takeoff Queues
This problem is based on a question in Larry Nyhoff’s book, “ADTs, Data Structures, and Problem
Solving Using C++”, and in particular Question 27 on Page 444. Here’s the basic idea of the
simulation. Consider an airport with one runway. At any given time during the day, there is a
queue of zero or more airplanes waiting to takeoff (because only one plane is allowed to use the
runway at a time). For example, another plane may be taking off, or another plane may be landing.
Thus, there is also a landing queue.
This is a simulation; so, it will involve a random number generator. This is meant to reflect reality
since we cannot predict exactly when a plane will arrive or depart due to numerous factors such as
weather, winds, the departure time at the previous airport, the spacing of planes in the sky (by air
traffic controllers), delays at the gate, the number of planes waiting to takeoff or land, contention
during taxiing (e.g., when two planes in the same proximity are both in the process of leaving their
respective gates to taxi to the runway), baggage handling backlog, security issues, plane de-icing,
The takeoff rate and landing rate (in number of planes per hour) are user-supplied inputs, with
priority given to landings. Write a program to simulate this airport’s operation. Assume a simulated
clock that advances in one-minute intervals. For each minute, generate two random numbers: If
the first number mod 60 is less than the landingRate (e.g., 10, which means 10 planes per hour)
then we will assume that a “landing” request has been generated, and that the plane is enqueued or
added to the landing queue; and if the second is less than takeoffRate, a “takeoff” request has
been generated, and the plane is added to the takeoff queue. Next, check whether the runway is
free. If it is, then first check whether the landing queue is non-empty, and if so, allow the first
airplane to land; otherwise, consider the takeoff queue. Have the program calculate the maximum
queue length and the average time that an airplane spends in a queue. For these statistics, you don’t
need to add an element (private member variable) to the LQueue class; you can simply increment
local counters using any reasonable interpretation for “average time”.
Note that even if the runway is free, and the queue is empty, a plane still has to enter the appropriate
queue, even if only for an instant. In such a case, if a plane is landing, the queue length is 1, and
the average wait time is zero (since it entered the queue at time t and was permitted to start landing
at time t in our simple simulation). A plane submitting a request to land at the 5-minute mark, and
actually being permitted to start landing at the 12-minute mark, has spent 7 minutes in the landing
queue (we don’t count the time it takes for a plane to actually perform the landing on the runway,
and we’ll assume that the plane only enters the landing queue when it is ready to land; otherwise,
it circles the airport while waiting).
Once a plane begins to takeoff, it finishes, even if a new plane requests to land before that plane
finishes its takeoff. If there are multiple planes in the landing queue, then they all get serviced
before a plane is allowed to takeoff. If a plane is taking off, and there is another plane in the takeoff
queue, you must make sure that the landing queue is still empty before releasing that next plane for
Your program might start as follows (the numbers are examples only):
bowen<221> runway
Time for a plane to land (in minutes): 3
Time for a plane to takeOff (in minutes): 2
Landing rate (planes per hour): 10
Takeoff rate (planes per hour): 12
How long to run the simulation (in minutes): 120
You can make up sequential identifiers (flight numbers) for planes, starting at 1000 (for example).
These numbers can be your data element in the LQueue class (see the bottom of the LQueue.h
file). Provide some running commentary in your output, so that the marker can understand what’s
going on. Here is an example of such comments (and the output from the program):

Time = 51
Plane 1007 wants to takeoff; added to takeoff queue; 1 in queue
Taking off: Plane 1007
Time = 52
Plane 1008 wants to land; added to landing queue; 1 in queue
Time = 53
Takeoff complete; 0 in queue
Plane 1009 wants to land; added to landing queue; 2 in queue
Plane 1010 wants to takeoff; added to takeoff queue; 1 in queue
Landing: Plane 1008
Time = 54
Time = 55
Plane 1011 wants to land; added to landing queue; 3 in queue
Time = 56
Landing complete; 2 in queue
Landing: Plane 1009

Time = 120
No new takeoffs or landings will be generated.

Time = 131
Takeoff complete; 0 in queue
End of program.
Maximum number of planes in landing queue was: 5
Average minutes spent waiting to land: 1.45
Maximum number of planes in takeoff queue was: 7
Average minutes spent waiting to takeoff: 6.333
In summary, loop through your program once per (simulated) “minute”, and check the queues. Be
sure to enqueue and dequeue any requests appropriately. You can use the remaining functions of
the LQueue class as you see fit.
Finally, be creative and create one additional, non-trivial feature to your application. For example,
you might want to incorporate one of the two functions from Part 1. The move_to_front
function isn’t hard to incorporate, so that might be worth 3-5% rather than 10%. However, the
second is more involved, assuming you manage two runways. Projects that go well beyond
expectations can earn a 5% bonus mark.
● Feel free to make any reasonable assumptions in your implementation, since there
probably are some details that are missing from the above specifications. In a README.txt
file, be sure to list any reasonable assumptions that you make, as well as any instructions
to the marker.
The C++ libraries you probably need are iostream, cstdlib, and ctime (for randomization).
The srand() and time() functions will be useful—the latter to seed the random number
generator—although you may wish to use a constant seed (e.g., “5” or some other number for
repeated random sequences during debugging).
Deliverables (to be submitted online, not on paper):
● All source code that you wrote (either .cpp or .C or .h files)
● A working Makefile so that the marker (and you) can compile the program.
● A README.txt file that gives any special instructions or comments to the marker:
o Your name or, if you have a programming partner, both your names
o Important: Only one partner should submit the files, but be sure to list both
students’ CS userids, names, and student numbers.
▪ Partners: Please make sure you communicate with each other as to who is
turning in the files—and when. You can always resubmit your files before
the due time. After the deadline, you’ll only get one submission attempt.
o Acknowledgment of any assistance you received from anyone but your team
members, the 221 staff, or the 221 textbooks, but please cite code quoted or
adapted directly from the texts (per the course’s Collaboration policy)
o A list of the files in your submission with a brief description of each file
o Any special instructions for the marker
● Two sample output files consisting of output from your testing of Part 1 and Part 2.
● Do reasonable error checking, but you don’t have to go overboard by checking for all kinds
of bad input conditions. You can assume that the user enters legitimate data.
● You must comment your code adequately (i.e., “reasonably”).
● And here is what you should not hand in: .o files, executables, core dumps, irrelevant stuff.
How to Use the Online “handin” Program
Please pay attention to the messages displayed on your screen during handin, to verify success.
All submissions—on-time or not—are timestamped.
1. Create a directory called ~/cs221/proj1 (i.e., create directory cs221 in your home directory,
and then create a subdirectory within cs221 called proj1).
2. To prepare to submit, first move or copy all of the files that you wish to hand in, to the proj1
directory that you created in Step 1.
3. Before the due deadline, hand in your directory electronically, as follows:
handin cs221 proj1
Note that you will receive a set of confirmation messages. If you don’t get any kind of an
acknowledgement, then you probably did something wrong. Please re-read the instructions and try
4. You can overwrite an earlier submission—unless it is now past the deadline—by including the
-o flag, and re-submitting, as follows:
handin -o cs221 proj1
You can hand in your files electronically as many times as you want. The latest timestamp will
determine your official handin time.
5. Additional instructions about handin, if you need them, are listed in the man pages (i.e., by
typing: man handin). At any time, you can see what files you have already handed in (and their
sizes) by typing the command:
handin -c cs221 proj1
Note: If your files have zero bytes, then something went wrong and you should run the original
handin command (without the -c) again.
6. To see the due dates and times for our course, type:
handin –l cs221
The first pair of dates and times is the actual deadline; the second pair is the last date and time after
which late assignments will no longer be accepted.