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详细说明： 数据结构第16次作业，hash表 Spellchecking Prerequisites, Goals, and Outcomes Prerequisites: Students should have mastered the following prerequisite skills. • Hash Tables - Understanding of the concept of a recursive function • Inheritance - Enhancing an existing data structure through specialization Goals: This assignment is designed to reinforce the student's understanding of the use of hash tables as searchable containers. Outcomes: Students successfully completing this assignment would master the following outcomes. • Familiarize how to use hash tables, specifically hash sets Background Any word processing application will typically contain a spell check feature. Not only does this feature point out potentially misspelled words; it also suggests possible corrections. Description The program to be completed for this assessment is a spell checker. Below is a screen shot of the program in execution? The program begins by opening a word list text file, specified by a command line parameter. The program outputs an error message and terminates if it cannot open the specified word list text file. A sample word list text file (wordlist.txt) is given in the supplied wordlist.zip archive. After successfully opening the specified word list text file, the program then stores each word into a hash table. The program then opens a file to spell check. This user specifies this file through the command line. After opening this file, the program then compares each word in the file against the words stored in the hash table. The program considers a word to be misspelled if the word does not exist in the hash table. When this occurs, the program displays the line number the word appeared in, the word, and a list of possible corrections. The list of possible corrections for a misspelled word is generated using a simple algorithm. Any variation of a misspelled word that is itself a word (i.e. it is found in the word list file) is a possible correction. Your solution to this assessment should consider the following variations of a misspelled word. • Transposing of adjacent letters For the misspelled word "acr", transposing adjacent letters yields the possible corrections of "car" and "arc". • Removal of each letter For example, removing each letter from the misspelled word "boaot" yields only the possible correction of "boat". Removing letters other than the second "o" does not generate a correctly spelled word. • Replacement of each letter For each character in a misspelled word, the program should check if the replacement with any letter generates a correctly spelled word. For the misspelled word "acr", replacing the "c" with an "i" yields "air", replacing the "r" with an "e" yields "ace", and so on. • Inserting any letter at any position in a word The program should consider if inserting any letter at any position in a misspelled word generates a correctly spelled word. For the misspelled word "acr", inserting an "e" after the "r" yields "acre". Files Following is a list of files needed to complete this assessment. • handout-files.zip contains all of the following necessary files: o main.cpp - This file contains the main routine. o hashset.h - This declares a hash set class. o hashset.cpp - This defines a hash set class. o dictionary.h - This file contains the partial definition of class Dictionary. Class Dictionary inherits from class HashSet. o wordlist.zip - This file is an archive that contains a word list text file. o test.txt - This is a sample text file that contains spelling errors. Tasks To complete this assessment, you need to complete the implementation of class Dictionary and complete the spell checking program contained in main.cpp. Following is an ordered list of steps that serves as a guide to completing this assessment. Work and test incrementally. Save often. 1. Begin by completing the definition of class HashSet. Class HashSet provide three functions to handle the hashset, search, insert, remove, which accept a single reference of key_type as a parameter. Search function: This function searches the key specified as the parameter in the hash table. If exist, return true, else return false. Note to use the eq which is a member of HashSet to compare two keys. Insert function: This function insert the key specified as the parameter to the hash set. Note to define the strategy of conflict and considerate the size of the hash set. Remove function: This function removes the key specified as the parameter from the hash set. Tips: refer to your textbook for the removing strategy. 2. Next, complete the definition of class Dictionary. Class Dictionary must provide a constructor that accepts a single string as a parameter. This parameter is the file name of the word list text file. This constructor must place all the words contained in the text file into the dictionary. Remember, class Dictionary is a type of HashSet, so use the inherited methods accordingly. 3. Next, complete the hash function encapsulated in class hash_function in dictionary.h. 4. Then, finish the implementation of function check_spelling. This function already contains code that reads a file line by line. It also extracts each word from a line using an instance of class stringstream. Your task is to check the spelling of each word. Use the inherited search function of class Dictionary to determine if a word exists in the dictionary. If the word exists in the dictionary, assume that it is spelled correctly. It if does not exist, assume it is misspelled. For each misspelled word, generate and display a list of possible corrections. (the generation of correction is given in the function create_suggestions, you can invoke this function) Note: the stl vector is used in this assignment, if you have any difficulties, you can refer to the documents given in this folder. Submission Submit only the following. 1. hashset.cpp – your completed class HashSet definiction 2. dictionary.h - your completed class Dictionary definition 3. dictionary.cpp - if created 4. main.cpp - your completed spell checker program ...展开收缩
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