CSC 17 Assignment: DNA Sequence Alignment with Dynamic Programming

	      Part II: Implementation and Testing

		      	Due Thursday 4/3



You MUST implement BOTH the "simple" and "advanced" scoring schemes as
described in the handout, and do it in a modular manner (such as using
inheritance).  I will NOT accept two different versions of the
program, one for each scoring scheme.  I will also be looking at your
code, and it should follow the outline you've agreed upon, unless there
was a significant problem no one could have forseen.


To test your program, you need to:

1. Print out the alignment and alignment score, such as:

CATTAATTACACTCTCGCACTCAC-CACCAAACATCCTA-AACCCAGACAGGCCTCGACTCC
 | |||  | |  ||||| ||  |  || |   |   || ||   |    ||| | ||| |
-ACTAAACA-AGACTCGC-CTGTCTAACTAGGGAGTTTATAATGAACCGTGGCGTAGAC-CA

Alignment score is 27

(sample was produced using the advanced scoring scheme)


2. Use small, hand crafted examples, such as (but not limited to):

   AATCG
   ATCAG    (checks if it figures out where to put the gaps)

********* For at least one example, you need to show how your program
generated output that corresponds to what you have worked out on paper.
You need to be able to print the matrix generated by your program, and show
that it corresponds to what you have done by hand.
*********


3. Use large, randomly generated sequences.  Test your program several times
before declaring that "it works". Be sure to use examples where the lengths
of the sequences are not the same.

Here's a function that will generate a random sequence of length n

    public static String randseq(int n)
    {
	String S = "";
	for(int i=1;i<=n;i++)
	    {
		int r = (int)(Math.random()*4);
		if (r==0) S += 'A';
		else if (r==1) S += 'C';
		else if (r==2) S += 'G';
		else S += 'T';
	    }
	return S;
    } // randseq

However, the above function assumes you're going to represent the
sequence as a String.  But you need to remember that the matrix actually
contains one more row and one more column, and you must adjust your
string and array indices accordingly.  Alternatively, you can use a
char[] array to represent the matrix, and align the coordinates to begin
with:

    public static char[] randseq(int n)
    {
	char[] S = new char[n+1]; // note one extra space added.
	for(int i=1;i<=n;i++)
	    {
		int r = (int)(Math.random()*4);
		if (r==0) S[i] = 'A';
		else if (r==1) S[i] = 'C';
		else if (r==2) S[i] = 'G';
		else S[i] = 'T';
	    }
	S[0] = '-';  // not really used
	return S;
    } // randseq


Notice that in the function above, the loop started at index 1 (which
means you need to allocate at least n+1 bytes to the array).  This is to
make the array coorespond to the matrix, which also must have an extra
row and column.

--------

String manipulations.  You will of course want to print the sequence as
a string.  Alternatively, you may choose to use a string to begin with
instead of a char[].  Consult the Java API documentation for the String
class, where you'll find many useful functions built-in.  For example,
given char[] A: String s= new String(A); will transform the array of
chars to a string, and s.toCharArray() will convert it back.   Strings 
have the advantage in that they can be easily modified.  For example,
s = 'A'+s; will add a new character to the front of the string.


-------

Using command-line arguments.  You'll notice that my program accepts
both numeric and char-based command-line arguments.  To tell the difference,
simply check the ascii value of the first character of the first argument.
That is, if args[0].charAt(0) > (int)'9' then the first argument is not
numeric.

------

Here's a problem that have caused me trouble in the past: when dealing
with a coordinate system, we usually think in terms of x, then y, or
column then row (this is how the tutorial refers to the coordinates).  But
in the C/C++ (and Java) programming language, 2D arrays are stored in 
row-major order, and we typically give the row (y) coordinate first.  Thus
your program may behave in a way that's different from how you envision it.
Be very careful, and consistent, with how you deal with array coordinates.

------

Extra Credit:  There is a flaw in the tutorial's "advanced scoring scheme" 
section.  Find and correct it.  Hint: during traceback, consider what
happens when one of x,y gets to 0, but the other one does not.