CSCI 311 – Spring 2012 - Program 1

Dynamic Hashing

Dr. Melody Stapleton, Instructor

Bonnie Varghese, Teaching Assistant

Due Date: All Program Components: Sunday, February 26, uploaded by midnight

Your TA, Bonnie, will provide the final input file(s) to run your program against by Thursday, Feb. 16.  Bonnie will also provide documentation, and style guidelines in the labs.

Your are to implement the Dynamic Hashing Algorithm, as discussed in class and posted in the course notes on the web using appropriate C++ classes. 

You are to structure your main program to accept and interpret file input according to the following:

Be sure to echo each input line of your input file immediately after reading that line.

You will need to write your program to first accept the power of 2 (from the input file, on the first line) that will be used for the hash function mod value.  Be sure to return the error: ”Value is not a power of 2” to the user if they do not enter a power of 2 and then halt execution of (exit) the program.  Return the error to the output file.  The next line on the input file will be the bucket size to be used for each bucket.

Listed below are the possibilities for the different categories of commands that will follow the above 2 lines:

• I      Integer_Key             To "insert" the integer to the appropriate Dynamic Hash structure bucket appropriately. It is an error to insert a duplicate value into your dynamic hash structure. Print out the message “Illegal attempt to insert duplicate value: “value”” on a single line should this occur. With a successful insertion print out the message “Successful Insertion of “value”” on one line, skip to the next line and print out the pseudokey, evaluated only to the extent necessary to place it in a bucket, followed by a space, followed by the entire contents of the bucket (separated by commas, printed on one line). The contents of the bucket should reflect the bucket AFTER you have accomplished the insertion. If your pseudokey has been fully expanded and your bucket is full, you will need to chain on a new bucket. In this case, Print out on one line first the pseudokey that the value hashed to, followed by a space, and then contents of each bucket, separated by commas. Between buckets print out the symbols “=>” and follow with the contents of the next bucket, etc. Should you be dealing with an insert into an empty hash structure, or a structure with only one bucket and room left in the bucket, print out “No pseudokey” followed by a space and the contents of the bucket after insertion, according to the rules above.
• D     Integer_Key To "delete" the integer from its Dynamic Hash structure bucket appropriately.  It is an error to attempt to delete a value that is not in your dynamic hash structure. Print out the message “Illegal attempt to delete a value not present: “value”” on a single line should this occur. Print out the message “Successful Deletion of “value”” on one line, skip to the next line and print out the phrase “Before:” followed by the pseudokey , evaluated only to the extent necessary to find it in a bucket, followed by a space and then entire contents of the bucket (separated by commas, printed on one line). Follow the rules for printing chained buckets as given above. If there is only one bucket in the hash then follow the “No pseudokey” printing rule described above. The reason you are printing out the Before deletion bucket(s) is that buckets may collapse and in fact no buckets may exist after certain deletions.
• S      Integer_Key To "search" for the integer key.  For a successful search print out the phrase: “Value found:” followed by the one of the following phrases – There are two cases: there is only one bucket and there is no tree structured directory or there is more than one bucket and there is a tree structured directory. If only one bucket and you found the element, print out on one line “No pseudokey” followed by a space and the contents of the bucket, separated by commas. If there is more than one bucket, print out the pseudokey, evaluated on to the extent necessary, of the bucket where you found the integer key, followed by a space and then print out the entire contents of the bucket on one line separated by commas..   For an unsuccessful search: 1) if the hash structure is empty, print out “Value not found: Hash is empty”. 2)If the hash structure has one bucket, print out “Value not found: No pseudokey” and the case of more than one bucket, 3) print out the pseudokey that you evaluated and the contents of the bucket (on one line separated by commas). If there is no bucket that is relevant for this pseudokey then print out the pseudokey, evaluated to the extent necessary, followed by a space and then phrase “no bucket” on one line. Again, follow the rules for printing chained buckets.
• P                                     To print out the contents of each bucket in the tree, by following an inorder traversal.   Print out the pseudokey for each bucket followed by a space, prior to printing out the contents of the bucket.  The first pseudokey to be printed will be all zeros, and then go from there with your inorder traversal steps. Follow the rules for printing out the contents of a single bucket and the rules for printing out chained buckets, should they occur. Print out each pseudokey along with its corresponding bucket (or chained buckets) on a separate line. If the Dynamic Hash structure is empty print out “Hash is empty”. If only the initial bucket has been allocated and no pseudokey evaluation was necessary print out “No pseudokey” followed by a space and then the contents of the bucket.

You will, of course, need to write a hash function, and you will need to create a Dynamic_Hash class that has at least the following member functions:

• Constructor
• Destructor
• Insert
• Delete
• Search
• Print

Note:  You will need to implement "chaining to overflow buckets" as discussed in class and shown in the course notes.

Output: Send your output for this program to a file.  Follow precisely the format for output described above.

Also Note: You are responsible to write a program that deals with *all cases*.  That is, your program should not only *work good on some input files*, it need to work on *all possible* input files.  This means it is not your TAs responsibility to give you an input file that allows your program to work.  It is your responsibility to write code that cannot be broken by any input file and so will work in all cases.  This will be the case for every program you write for this course.

A sample file follows that adheres to the input file format: In the left column you find the values in the input file. In the right hand column is the correct output for this sequence of input.

Your homework for Thursday, 2/3/2012 is to finish off this output listing!!!

Input on left: Output that should be generated from this input:

8	8
2	2
P	P
	Hash is empty
D 100	D 100
	Illegal attempt to delete a value not present: 100
S 99	S 99
	Value not found: Hash is empty
I 46	I 46
	Succesful insertion of 46 No pseudokey 46
P	P
	No pseudokey 46
I 55	I 55
	Successful insertion of 55 No pseudokey 46, 55
I 46	I 46
	Illegal attempt to insert duplicate value: 46
I 88	I 88
	Successful insertion of 88 0 88
P	P
	0 88 1 46, 55
S 46	S 46
	Value found: 1 46, 55
S 99	S 99
	Value not found: 0 88
I 99	I 99
D 50	D 50
S 99	S 99
I 200	I 200
P	P
D 55	D 55
P	P
I 121	I 121
I 201	I 201
I 300	I 300
I 400	I 400
I 500	I 500
S 300	S 300
P	P
D 500	D 500
D 46	D 46
P	P
D 200	D 200
D 88	D 88
P	P
D 121	D 121
D 99	D 99
P	P
D 300	D 300
D 400	D 400
D 201	D 201
P	P