This is the archived website of SI 335 from the Spring 2016 semester. Feel free to browse around; you may also find more recent offerings at my teaching page.

Project 3: The Battlefield

  • Due Date: 23:59 on Monday, April 25

This project contains only electronic parts. You code must be submitted according to the instructions on the submit page prior to the deadline.

  • Review the course policy on academic integrity for programming projects. Be sure to cite any discussions with classmates, or any online resources that you used. Citations should appear in comments in your code, and in README.txt files that you submit.
  • Part of your grade will be based on "coding style". This is mostly about whether your code is easy to follow, consistently formatted, and sensibly designed. You should use meaningful variable/function/class names, clearly explain what is going on in your code, and "clean up" any extra debugging or non-functional parts before submitting.
  • Be sure to follow the exact input/output specifications and filename conventions as specified. You should write any error or debugging messages to stderr (cerr), as this stream will be ignored in testing.
  • Your program will automatically compiled and tested by a variety of exciting bash scripts. This means that it is imperative that your code compiles without errors in the CS linux lab environment and that it behaves exactly as specified. You should make use of the 335sanity check program to help make sure everything works.

1 Battlefield Planning

Now the general who wins a battle makes many calculations in his temple ere the battle is fought. The general who loses a battle makes but few calculations beforehand. Thus do many calculations lead to victory, and few calculations to defeat; how much more no calculation at all! It is by attention to this point that I can foresee who is likely to win or lose.

—Sun Tzu, The Art of War

In this project, you are going to find optimal or nearly-optimal paths for some number of assets to acquire a number of targets in a battlefield, while avoiding some obstacles.

The basic idea is this: The assets each move around the battlefield at the same time. They are trying to go to each target in order to get points. Your task is to make a plan for how the assets will move around.

Moving: Only the assets move; the targets and obstacles stay in place. At each step, every asset moves one space either up, down, left, or right. If an asset moves into a space with a target, you get the points for that target (see below). If an asset moves into a space with an obstacle, that asset is gone and any further moves of the asset are ignored. Same if the asset moves outside of the boundaries.

Scoring: Each target starts with a value, which will be some positive integer. At each step, the value of every remaining target goes down by one. The battle ends when all targets have been acquired, or all their values have gone down to zero, or all assets have run into obstacles, or your plan has run out of moves.

Your task is to read in a description of the map (dimensions, obstacles, assets, and targets) and output a series of moves for all the assets to take in parallel, in order to acquire the targets as quickly as possible. The goal is to get the highest score, which is the total value of all targets at the time you acquire them.

2 Input and output

The input to your program will be a single file that stores a "map" specifying the battlefield dimensions, the number and locations of any obstacles, the number and locations of any assets, and the number, location, and value of any targets.

Specifically, the input map file consists of four parts:

  1. Dimensions: Two integers for the number of rows and columns in the battlefield,
  2. Obstacles: An integer for the number of obstacles, followed by that many pairs of integers for the coordinates of each obstacle.
  3. Assets: An integer for the number of assets, followed by that many pairs of integers for the starting coordinates of each asset.
  4. Targets: An integer for the number of targets, followed by that many triples of integers, indicating the row index, column index, and value of each target.

The output from your program will be in a file specifying the "moves" that each asset should make in order to reach the targets quickly. Specifically, your output will consist of a number of lines, one per step. On each line, there will be k directions, where k is the number of assets. Each direction is either U, D, L, or R. Note it is not allowed for an asset to stand still!

3 Example

Here is an example map file:

10 12

0 6
3 5
4 6
4 7
4 10
5 2
7 3

0 8
9 3

0 9 36
2 9 95
4 5 56
5 9 56
6 5 88
6 7 81
7 6 12
8 5 76
9 0 60
9 4 96
9 5 74

You can see that the file above is split into 4 parts:

  1. Dimensions: The map has 10 rows and 12 columns.
  2. Obstacles: The map has 7 obstacles, at the specified coordinates.
  3. Assets: There are 2 assets, at the specified coordinates.
  4. Targets: There are 11 targets, at the specified coordinates. Each target also has a specified starting value.

A visual representation of this map (which you could see yourself by running python3 <map_file>) is below. The obstacles are black diamonds, the assets are the numbered blue squares, and the targets are the letters in magenta.

Notice: rows and columns are numbered from 0, starting at the top-left corner.

The output from your program will be a list of moves for the assets. For the map above, it might look something like this:


You can see there are a number of lines, and on each line there is one direction for each of the assets to move in. So the first line above says asset 1 should move one space to the right, and asset 2 should move 1 space to the left. On step 2, asset 1 changes direction to move down, and asset 2 keeps moving left. They both keep going in the same direction on step 3.

Here's what those three steps look like on the map. (You could see this by running python3 <map_file> <moves_file>.)

4 Limitations and assumptions

You may assume the map files always fall within the following limits:

  1. Each dimension is at least 1 and at most 200.
  2. The number of assets is at least 1 and at most 3
  3. The number of targets is at most 26.

You can implement your solution in C++, Python, or Java (or something else if you talk to Dr. Roche about it). In any case, it must complete execution and output all the moves within 30 seconds runtime. Of course, it's OK if it's faster than that!

Initially, you may assume that all obstacles, targets, and assets are in distinct locations. Assets are not allowed to move onto obstacles, but they can move into the same square as each other if you want to do that for some reason. Keep in mind, you only get points for a target the first time any asset reaches that target.

5 README file

Your submission must include a README.txt file with at least the following information:

  • Any outside resources you used
  • A high-level description of how your program works. I don't need pseudocode here, but it should explain your algorithm, what kinds of algorithms or ideas from class it uses, and what kinds of data structures you are using.
  • What algorithm design paradigms did you employ in designing your algorithm?
  • Give some discussion of what the big-Oh runtime of your program is. It's OK if you don't have something totally exact here, but be as specific as you can.

6 Starter code

There is no starter code for the plan program that you are going to write. You really get to write it yourself, from scratch!

The following three Python programs should be helpful in testing and developing your code. The program will generate a random map with the specified dimensions and number of obstacles, assets, and targets. The program will make a nice visual "movie" of your moves, along with the scores, so you can see what your program is producing. The program does the same, but there's no visual component, just the scores. This is mostly useful for when you get into the bigger maps that might be too large to fit on the screen visually.

You can get all these files at once by downloading the file proj3.tar.gz and running tar xzvf proj3.tar.gz

You run each of these programs by typing, for example, python3 They all have nice help messages if you run them with the -h flag.

7 Submission instructions

Submit according to the normal instructions on this page. You have a choice of programming in Java, C++, or Python. In any case, your program will take two command-line arguments. The first will specify the map filename (your input), and the second will specify the moves filename (your output).

Java specifics

Put your main() method in a class called Plan in a file called You can also submit any other .java files you like, and you also need to submit your README.txt. I will compile and run your program like:

$ javac *.java
$ java Plan mapfile movesfile

C++ specifics

Put your main() method in a file called plan.cpp. You can also submit any other .cpp or .h files you like, and you also need to submit your README.txt. I will compile and run your program like:

$ g++ -O3 -std=c++11 *.cpp -o plan
$ ./plan mapfile movesfile

Python specifics

Put your main program in a file called You can also submit any other .py files you like, and you also need to submit your README.txt. I will run your program like:

$ python3 mapfile movesfile

8 Grading

Your program will be tested on a variety of maps ranging from the smallest possible, with one asset and few obstacles and targets, to the largest possible 200x200 with three assets, many obstacles, and 26 targets.

Remember, your program has to finish within 30 seconds on any input file. Otherwise, you won't get any points for that map.

After running your plan program, I will use the program, along with the map file, to find out how many points your "moves" score. Say your moves score \(x\) points. After looking at all of the sumbissions, as well as my sample solutions, I will also get the maximum number of points any of them score on that map file, which I will call \(m\). Your grade for that map will be determined from the ratio \(\frac{x}{m}\) of your points divided by the maximum number of points for that map. There will be bonus points available on every sample map, if you get the maximum number of points (or close to it).

As usual, besides these auto-tests, your program will also be graded on readability, documentation, and code organization. Follow the "coding guidelines" outlined at the beginning of this page.