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讲解CSE 101 程序 辅导 Data Structures

Introduction to Data Structures and Algorithms
Programming Assignment 8

In this project you will re-create the Dictionary ADT from pa7, but now based on a Red-Black Tree. Red
black trees are covered in Chapter 13 of the text, and will be discussed at length in lecture. All relevant
algorithms for RBTs (and BSTs) are posted on the webpage under Examples/Pseudo-code. Aside from
having a RBT as its underlying data structure, your Dictionary ADT will have only slight changes to its
interface. The recommended approach for this project is to just copy Dictionary.cpp from pa7 and make
the necessary changes, but you can start from scratch if you feel it is necessary. The header file Dictionary.h
is posted in Examples/pa8. It's most significant difference from the header file for pa7 is a new Node field
of type int called color. Other than that, the only difference is a new section for RBT helper functions.
Although these functions are listed as optional, and you may make changes as you like, you should consider
them as absolutely necessary for this project.

You will create two top-level clients in this assignment. The first will be called Order.c, with the same
specifications as in pa7. No changes should be necessary from that project. Again, five pairs of input-
output files are given in Example/pa8, along with a random input file generator. Note that the input files
are identical to those of pa7, but the paired outputs are different. In particular, the output file sections giving
all keys in a pre-order traversal are different, since the trees are now balanced by the RBT algorithms.

The second top-level client will be called WordFrequency.cpp. It will read in each line of a file, parse the
individual words on each line, convert each word to all lower case characters, then place it (as key) in a
Dictionary. Individual words in the input file may be repeated however. The number of times a given word
is encountered (its frequency) will also be stored (as value) in the Dictionary. Thus, as your program is
reading in words, it should first check to see if the word (key) is already present, using contains(). If it
is a new word, add it using setValue(). If it already exists, increment the corresponding value by calling
getValue(). Recall that the getValue() function returns a reference to a value, which can then be used
to alter that value. Use the example FileIO.cpp posted in /Examples/C++/FileIO as the starting point for
WordFrequency.cpp, since much of what you need is already there. The program FileIO.cpp contains a
string variable called delim, which is initialized to be a single space.

string delim = " ";

This is the delimiter used by the string functions find_first_of() and find_first_not_of() to
determine which characters belong to tokens, and which do not. Thus FileIO.cpp tokenizes the file around
spaces. Your program WordFrequency.cpp will instead tokenize around a larger set of characters. The
words in our file will be substrings that contain only alphabetic characters. To accomplish this, you can
reset delim as follows.

string delim = " \t\\\"\',<.>/?;:[{]}|`~!@#$%^&*()-_=+0123456789";

So, to parse the input file, remove all whitespace, punctuation and special characters. What's left are the
words to be placed in the Dictionary, along with their frequencies.

Once all the words from an input file are placed in the Dictionary, along with their frequences, your program
WordFrequency.cpp will print the Dictionary to the output file. The folder /Examples/pa8/ contains two
very large text files called Shakespeare (containing the complete works of William Shakespeare) and
Gutenberg (containing several English language texts provided by Project Gutenberg). Also included are
the corresponding output files Shakespeare-out and Gutenberg-out. Use these to test WordFrequency.cpp.
Also, as before, a test client called DictionaryClient.cpp is posted in Examples/pa8. This program is more
extensive than the pa7 version, as it tests the remove() operation much more thoroughly. You should still
consider it a weak test of the Dictionary ADT however, and as always, design your own tests. There is one
very small change from pa7 that should be mentioned. The pre-condition error messages for operations
next() and prev() are worded slightly differently (so as to be consistent with those of currentKey()
and currentVal().) These changes will be apparent from the output file DictionaryClient-out, which is
also included in Examples/pa8.

Altogether this should be a straightforward assignment, especially if pa7 went well for you. Submit the
following 7 files in the usual manner before the end of the grace period.

README Written by you, a catalog of submitted files and any notes to the grader
Makefile Provided, alter as you see fit
Dictionary.h Provided, you may alter the "helper functions" sections, but nothing else
Dictionary.cpp Written by you, the majority of work for this project
DictionaryTest.cpp Written by you, your test client of the Dictionary ADT
Order.cpp Written by you, a client for this project, unchanged from pa7
WordFrequency.cpp Written by you, a client for this project

As usual, do not turn in any executable files, binaries, or anything not listed above. Good luck.

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