私は以前に投稿し、二重にリンクされたリストをディープ コピーする方法を理解するのに役立ちました。現在、アクセス違反「0xC000000005」の問題が発生しています。これは、null ポインターを参照しようとする試みが原因であると考えられます。これは宿題であり、私は C++ を初めて使用するので、誰かが私に作業コードを提供するのではなく、どこが間違っているのかを理解するのに助けが欲しい.
これが私の教授から与えられた私のインターフェイスです。いかなる方法でも変更することはできません。
#ifndef TEXTANALYZER_H
#define TEXTANALYZER_H
#include <iostream>
#include <string>
using namespace std;
class TextAnalyzer {
private:
/*
* Class: Node
*
* This class represents a node in a sorted doubly linked list that stores a
* list of words and their frequency of occurrency.
*/
class Node {
public:
string word;
int wordFrequency;
Node* previous;
Node* next;
Node(const string& word,
const int wordFrequency,
Node* const previous,
Node* const next)
: word(word),
wordFrequency(wordFrequency),
previous(previous),
next(next)
{}
}; // end ListNode
/*********************************************************************/
Node* head;
Node* tail;
/*
* Releases all the memory allocated to the list.
*/
void releaseNodes();
/*
* Makes a deep copy of the object.
*/
void copyNodes(Node* const copyHead);
/*
* Returns a populated Node.
* Throws a bad_alloc exception if memory is not allocated.
*/
Node* createNode(const string& word,
const int wordFrequency,
Node* const previous,
Node* const next);
public:
/*
* Initializes head and tail, each to a dymmy node.
*/
TextAnalyzer();
/*
* Makes a deep copy of the object passed in.
* Calls copyNodes() to do the actual work.
*/
TextAnalyzer(const TextAnalyzer& copyObject);
/*
* Releases all the memory allocated to the object.
* Calls the releaseNodes() method to do the actual work.
*/
~TextAnalyzer();
/*
* Makes a deep copy of the rhs object.
*/
TextAnalyzer operator =(const TextAnalyzer& assignObject);
/*
* Inserts the word in a sorted order into the list.
*
* If no Node exists with that initial character, one is added in
* sorted order. If one does exist (same word), then the word frequency
* of that word is incremented by one.
*/
void insertWord(const string& word);
/*
* Returns a count of all the words in the list.
*/
int wordCount() const;
/*
* Returns a count of all the words with the initial character.
*/
int wordCountWithInitialCharacter(const char startsWith);
/*
* Returns a description of the object. The string is formatted as:
* [A words:]
* [<word>(<count>)]
* [<word>(<count>)]
* ...
*
* [B words:]
* [<word>(<count>)]
* [<word>(<count>)]
* ...
*
*...
*/
string toString() const;
};
#endif
これが私のクラス定義です：
#include "textAnalyzer.h"
#include <string>
#include <iostream>
#include <sstream>
TextAnalyzer::Node* TextAnalyzer::createNode(const string& word, const int wordFrequency,
Node* const previous, Node* const next)
{
return new Node(word, wordFrequency, previous, next);
}
void TextAnalyzer::releaseNodes()
{
Node* del = tail;
while(tail != NULL)
{
tail = tail->previous;
tail->next = del;
delete del;
del = tail;
}
delete [] head;
delete [] tail;
head = tail = del = NULL;
}
void TextAnalyzer::copyNodes(Node* const copyHead)
{
head = new Node(*copyHead);
Node* iter = head->next;
for(Node* np = copyHead->next; np != NULL; np = np->next)
{
iter->next = new Node(*np);
iter = iter->next;
}
iter = NULL;
}
TextAnalyzer::TextAnalyzer():head(createNode("0",0,NULL,NULL)),tail(head)
{}
TextAnalyzer::TextAnalyzer(const TextAnalyzer& copyObject)
{
copyNodes(copyObject.head);
}
TextAnalyzer::~TextAnalyzer()
{
releaseNodes();
}
TextAnalyzer TextAnalyzer::operator=(const TextAnalyzer& assignObject)
{
return TextAnalyzer(assignObject);
}
void TextAnalyzer::insertWord(const string& word)
{
Node* iter = head->next;
while(iter != NULL)
{
if(iter->word == word)
iter->wordFrequency++;
else if(iter->word[0] == word[0] && iter->next != NULL)
{
Node* temp = iter->next;
iter->next = createNode(word, 1, iter, temp);
iter = iter->next;
temp->previous = iter;
temp = NULL;
}
else if(iter->word[0] == word[0] && iter->next == NULL)
{
iter = createNode(word, 1, tail, NULL);
tail = iter;
}
else
iter = iter->next;
}
iter = NULL;
}
int TextAnalyzer::wordCount() const
{
Node* iter = head->next;
int count = 0;
while(iter != NULL)
count++;
return count;
}
int TextAnalyzer::wordCountWithInitialCharacter(const char startsWith)
{
Node* iter = head->next;
int count = 0;
for(int i = 0; i < wordCount(); i++)
{
if(startsWith == iter->word[0])
count++;
iter->previous = iter;
iter = iter->next;
}
iter = NULL;
return count;
}
string TextAnalyzer::toString() const
{
Node* iter = head->next;
string desc = "List of words: \n";
ostringstream convert;
for(int i = 0; i < wordCount(); i++)
{
convert << iter->word[0] << " words:\n"
<< iter->word << "("
<< iter->wordFrequency
<< ")\n";
iter->previous = iter;
iter = iter->next;
}
iter = NULL;
return desc + convert.str();
}
デバッガーによると、私の releaseNodes() メソッドで問題が発生します。コメントを追加して、それが発生する特定の行を指摘しました。
void TextAnalyzer::releaseNodes()
{
Node* del = tail;
while(tail != NULL)
{
tail = tail->previous; //debugger flags this line when error occurs
tail->next = del;
delete del;
del = tail;
}
delete [] head;
delete [] tail;
head = tail = del = NULL;
}
アクセス違反の原因はわかりませんが、私が言ったように、私は C++ が初めてです。ありとあらゆる助けをいただければ幸いです。