ESc101 Laboratory Assignment 
	        	Tuesday of Week of 25/10/04

Write a program to sort "N" (a power of 2) integers stored in a file, say FileA.dat using 
Iterative Merge Sort.

The sorting algorithm is as follows: 
	- Consider original list as N sublists of size 1.
	- Scan through list performing 1-by-1 mergers to produce N/2 sorted
	  sub-lists of 2 elements
	- Scan through list performing 2-by-2 mergers to produce N/4 sorted 
	  sub-lists of 4 elements and so on.
In each step merge first and second sub-list, third and fourth sub-list so on.
For example, suppose the list to be sorted is : 23  13  14  26  19  11  16  17
Then, get (8/2=)4 sorted sublists as: 13 23   14 26   11 19   16 17
Now, (8/4=)2 sorted sublists as: 13 14 23 26    11 16 17 19
Now, (8/8=)1 sorted list as: 11 13 14 16 17 19 23 26

How to merge two sorted sublists:
Keep an index-pointer (index varible) pointing at the first element of
each sublist. Compare the two elements and output the smaller. Then increment
the pointer of the sub-list from where we output. For example
 to merge   13 14 23 26    and    11 16 17 19    and output = empty
            |                     |

next step   13 14 23 26    and    11 16 17 19    and output=  11
            |                        |

next step   13 14 23 26    and    11 16 17 19    and otuptu=  11 13
               |                     |
so on...


Use of arrays is not allowed. Use a second file, FileB.dat for 
The sorting algorithm is as follows: 
the process as described below. 

In the first iteration, read from FileA.dat and write into FileB.dat.
In the second iteration read from FileB.dat and write into FileA.dat. In 
this way alternate till sorting is complete. If final result ends up in 
FileB.dat, then copy it in FileA.dat.

Open the file FileA.dat twice because you need to maintain two indices into the file. 
They should point to the beginning of the two sublists(of size say s) currently being 
considered for merging. The merged list is written to the second File. After one iteration,
the partly sorted file is now in FileB.dat. Now adjust the two indices in
FileB.dat properly and repeat the above process. 

Note that the above method should be other than "main". Then in the "main"
method call the sort method. You should use text-file so that you can create
the data-file directly.

Q: Can you modify your program to deal with any N? If you have time, then
try it.