这个双链表的移除函数存在分割错误。在linux终端中使用gdb调试显示
1)只有第一个条件if(curr->prev == NULL)，要删除的节点是到达列表中的第一个节点。
2)在delete curr命令下，程序进入对数据对象建模的类的析构函数，在delete title命令下中断。
在实现user6545984答案后，唯一的问题是else if(curr->next == NULL)条件下tail = tail->prev上的分割错误。程序无法通过此条件语句。
另外，下面还添加了其他代码。很抱歉这么长。
add和remove函数的代码，以及析构函数的代码:
添加函数(创建双链表)
void SongList::addSongSorted(const Song &aSong)
{
char title[MAX_CHAR];
char currTitle[MAX_CHAR];
aSong.getTitle(title);
Node * newNode = new Node(aSong);
Node * prev = NULL;
Node * curr = head;
while(curr)
{
curr->song.getTitle(currTitle);
if(strcmp(title, currTitle) < 0)
break;
prev = curr;
curr = curr->next;
}
newNode->next = curr;
newNode->prev = prev; //Added due to answer. See edit note.
if(!prev)
head = newNode;
else
{
prev->next = newNode;
}
size++;
}
void SongList::remove(const Song& aSong)
{
Node *curr = head;
int indexRem = 0;
int j = 0;
//get the index to remove
cout << "Enter the index to remove.n";
cout << "This value can be obtained via the list all functionality.n";
cin >> indexRem;
while(indexRem > getSize()|| indexRem < 0)
{
cout << "Enter a valid index to remove.n";
cin >> indexRem;
}
while(curr && j < indexRem)
{
curr=curr->next;
j++;
}
if(!curr)
{
cout << "didnt find anything" << endl;
}
else
{
if(curr->prev == NULL) //NOTE: this is the only condition ever engaged
{
head = head->next;
head->prev = NULL;
delete curr; //NOTE: goes to destructor
curr = NULL;
}
else if(curr->next == NULL)
{
tail = tail->prev; //EDIT: only issue is seg fault here
tail->next = NULL;
delete curr;
curr = NULL;
}
else
{
Node * previous = curr->prev;
Node * following = curr->next;
previous->next = following;
following->prev = previous;
delete curr;
}
}
析构函数(现在请忽略)
Song::~Song()
{
if(title != NULL)
delete [] title; //Breaks here
if(artist != NULL)
delete [] artist;
if(album != NULL)
delete [] album;
}
对象类
头文件#ifndef SONG_H
#define SONG_H
#include<cstring>
#include<stdio.h>
#include<cstdlib>
const int MAX_CHAR = 101;
const int SONG_CAPACITY = 100;
class Song
{
public:
//constructors
Song();
Song(const char title[], const char artist[], const char album[], int min, int sec);
//Destructor
~Song();
//accessor functions
void getTitle(char title[]) const;
void getArtist(char artist[]) const;
void getAlbum(char album[]) const;
int getMin()const;
int getSec()const;
void print() const;
//mutator functions
void setTitle(const char title[]);
void setArtist(const char artist[]);
void setAlbum(const char album[]);
void setMin(int &min);
void setSec(int &sec);
private:
char* title;
char* artist;
char* album;
int min;
int sec;
};
#endif
对象类
源文件 #include "song.h"
#include <iostream>
using namespace std;
Song::Song()
{
title = new char[strlen("no title")+1];
strcpy(title, "no title");
artist = new char[strlen("no artist")+1];
strcpy(artist, "no artist");
album = new char[strlen("no album")+1];
strcpy(album, "no album");
min = 0;
sec = 0;
}
Song::Song(const char title[], const char artist[], const char album[], int min, int sec)
{
this->title = new char[strlen(title)+1];
strcpy(this->title, title);
this->artist = new char[strlen(artist)+1];
strcpy(this->artist, artist);
this->album = new char[strlen(album)+1];
strcpy(this->album, album);
this->min = min;
this->sec = sec;
}
Song::~Song()
{
if(title != NULL)
delete [] title;
if(artist != NULL)
delete [] artist;
if(album != NULL)
delete [] album;
}
void Song::getTitle(char title[]) const
{
strcpy(title, this->title);
}
void Song::getArtist(char artist[]) const
{
strcpy(artist, this->artist);
}
void Song::getAlbum(char album[]) const
{
strcpy(album, this->album);
}
int Song::getMin()const
{
return min;
}
int Song::getSec()const
{
return sec;
}
void Song::print() const
{
cout << title << 't'
<< artist << 't'
<< album << 't'
<< min << 't'
<< sec << endl;
}
void Song::setTitle(const char title[])
{
if(this->title != NULL)
delete [] this->title;
this->title = new char[strlen(title)+1];
strcpy(this->title, title);
}
void Song::setArtist(const char artist[])
{
if(this->artist != NULL)
delete [] this->artist;
this->artist = new char[strlen(artist)+1];
strcpy(this->artist, artist);
}
void Song::setAlbum(const char album[])
{
if(this->album != NULL)
delete [] this->album;
this->album = new char[strlen(album)+1];
strcpy(this->album, album);
}
void Song::setMin(int &min)
{
this->min = min;
}
void Song::setSec(int &sec)
{
this->sec = sec;
}
###Header file for object management class
#ifndef SONG_LIST
#define SONG_LIST
#include "song.h"
#include <iostream>
using namespace std;
class SongList
{
public:
SongList();
SongList(const char fileName[]);
~SongList();
bool get(int index, Song& aSong) const;
//Search function declaration
void searchArtist(const char artist[], Song& match) const;
void searchAlbum(const char album[], Song& match) const;
int getSize() const;
void printAll() const;
void saveToFile(const char fileName[]) const;
void addSong(const Song& aSong);
// void addAtStart(const Song& aSong);
// void append(const Song& aSong);
void addSongSorted(const Song& aSong);
void loadFromFile(const char fileName[]);
void remove(const Song& aSong);
private:
struct Node
{
Song song;
Node * next;
Node * prev;
Node(const Song& aSong)
{
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
aSong.getTitle(title);
aSong.getArtist(artist);
aSong.getAlbum(album);
min = aSong.getMin();
sec = aSong.getSec();
song.setTitle(title);
song.setArtist(artist);
song.setAlbum(album);
song.setMin(min);
song.setSec(sec);
next = NULL;
}
};
Node * head;
Node * tail;
int size;
};
#endif
###Source file for object management class
#include "songlist.h"
#include <iostream>
#include <fstream>
#include <iomanip>
#include <cstring>
using namespace std;
//Ok as is
SongList::SongList()
{
head = NULL;
tail = NULL;
size = 0;
}
//OK as is
SongList::SongList(const char fileName[])
{
head = NULL;
tail = NULL;
size = 0;
loadFromFile(fileName);
}
//Needs modification to deconstruct tail...
SongList::~SongList()
{
Node * curr = head;
while(head != NULL)
{
curr = head->next;
delete head;
head = curr;
}
}
//OK as is
void SongList::loadFromFile(const char fileName[])
{
ifstream in;
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
Song aSong;
in.open (fileName);
if(!in)
{
in.clear();
cerr << endl << "Fail to open "
<< fileName << " for input!" << endl << endl;
exit(1);
}
//cout << "loading point reached" << endl;
in.getline(title, MAX_CHAR, ';');
while (!in.eof())
{
//cout << "check input from file" << endl;
in.getline(artist, MAX_CHAR, ';');
in.getline(album, MAX_CHAR, ';');
in >> min;
in.ignore(MAX_CHAR, ';');
in >> sec;
in.ignore(MAX_CHAR, 'n');
aSong.setTitle(title);
aSong.setArtist(artist);
aSong.setAlbum(album);
aSong.setMin(min);
aSong.setSec(sec);
addSong(aSong);
// aSong.print();
in.getline(title, MAX_CHAR, ';');
}
in.close();
}
//Ok as is
int SongList::getSize()const
{
return size;
}
bool SongList::get(int index, Song &aSong) const
{
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
if(index < 0 || index >= size)
return false;
int i;
Node * curr = head;
for(i = 0; i < index; i++)
{
curr = curr->next;
}
curr->song.getTitle(title);
curr->song.getArtist(artist);
curr->song.getAlbum(album);
curr->song.getMin();
curr->song.getSec();
aSong.setTitle(title);
aSong.setArtist(artist);
aSong.setAlbum(album);
aSong.setMin(min);
aSong.setSec(sec);
return true;
}
//OK as is
void SongList::searchArtist(const char artist[], Song& match) const
{
Node * curr;
char currentTitle[MAX_CHAR];
char currentArtist[MAX_CHAR];
char currentAlbum[MAX_CHAR];
int currentMin;
int currentSec;
for(curr = head; curr != NULL; curr = curr->next)
{
curr->song.getTitle(currentTitle);
curr->song.getArtist(currentArtist);
curr->song.getAlbum(currentAlbum);
curr->song.getMin();
curr->song.getSec();
if(strcmp(artist, currentArtist) == 0)
{
cout << "Found: " << currentTitle << 't'
<< currentArtist << 't'
<< currentAlbum << 't'
<< currentMin << ':'
<< currentSec << endl;
}
}
}
//Ok as is
void SongList::searchAlbum(const char album[], Song &match) const
{
Node * curr;
char currentTitle[MAX_CHAR];
char currentArtist[MAX_CHAR];
char currentAlbum[MAX_CHAR];
int currentMin;
int currentSec;
for(curr = head; curr != NULL; curr = curr->next)
{
curr->song.getTitle(currentTitle);
curr->song.getArtist(currentArtist);
curr->song.getAlbum(currentAlbum);
curr->song.getMin();
curr->song.getSec();
if(strcmp(album, currentAlbum) == 0)
{
cout << "Found: " << currentTitle << 't'
<< currentArtist << 't'
<< currentAlbum << 't'
<< currentMin << ':'
<< currentSec << endl;
}
}
}
//OK as is
void SongList::printAll() const
{
Node * curr;
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
int index = 0;
for(curr = head; curr != NULL; curr = curr->next)
{
curr->song.getTitle(title);
curr->song.getArtist(artist);
curr->song.getAlbum(album);
min = curr->song.getMin();
sec = curr->song.getSec();
cout << index << " " << title << " "
<< artist << " " << album << " "
<< min << ':' << sec << endl;
index++;
}
}
//OK as is
void SongList::saveToFile(const char fileName[])const
{
ofstream out;
Node* curr;
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min = 0;
int sec = 0;
out.open(fileName);
if(!out)
{
out.clear();
cerr << endl << "Fail to open" << fileName << ". Check your directory." << endl << endl;
exit(1);
}
for(curr = head; curr; curr = curr->next)
{
curr->song.getTitle(title);
curr->song.getArtist(artist);
curr->song.getAlbum(album);
min = curr->song.getMin();
sec = curr->song.getSec();
out << title << ';' << artist << ';' << album << ';' << min << ';' << sec << endl;
}
out.close();
}
void SongList::addSong(const Song &aSong)
{
addSongSorted(aSong);
}
//Don't think I need this
/*
void SongList::addAtStart(const Song &aSong)
{
Node * newNode = new Node(aSong);
newNode->next = head;
head = newNode;
size++;
}
//...or this
void SongList::append(const Song &aSong)
{
Node * newNode = new Node(aSong);
if(!head)
head = newNode;
else
{
Node * curr = head;
while(curr->next)
{
curr = curr->next;
}
curr->next = newNode;
}
size++;
}
*/
void SongList::addSongSorted(const Song &aSong)
{
char title[MAX_CHAR];
char currTitle[MAX_CHAR];
aSong.getTitle(title);
Node * newNode = new Node(aSong);
Node * prev = NULL;
Node * curr = head;
while(curr)
{
curr->song.getTitle(currTitle);
if(strcmp(title, currTitle) < 0)
break;
prev = curr;
curr = curr->next;
}
newNode->next = curr;
newNode->prev = prev;
if(!prev)
head = newNode;
else
{
prev->next = newNode;
}
// printAll();
size++;
}
void SongList::remove(const Song& aSong)
{
Node *curr = head;
int indexRem = 0;
int j = 0;
cout << "Enter the index to remove.n";
cout << "This value can be obtained via the list all functionality.n";
cin >> indexRem;
while(indexRem > getSize()|| indexRem < 0)
{
cout << "Enter a valid index to remove.n";
cin >> indexRem;
}
while(curr && j < indexRem)
{
curr=curr->next;
j++;
}
if(!curr)
{
cout << "didnt find anything" << endl;
}
else
{
if(curr->prev == NULL)
{
head = head->next;
head->prev = NULL;
delete curr;
curr = NULL;
}
else if(curr->next == NULL)
{
tail = tail->prev;
tail->next = NULL;
delete curr;
curr = NULL;
}
else
{
Node * previous = curr->prev;
Node * following = curr->next;
previous->next = following;
following->prev = previous;
delete curr;
}
}
size--;
}
有什么建议吗?
您在添加新节点时忘记了->prev指针，这使得if(curr->prev == NULL)始终为true。只需在addSongSorted()函数中添加newNode->prev = prev;。
顺便说一下，在删除节点时可能需要--size。
这会给你一个错误，因为你不应该使用new或new[]而使用delete或delete[]。New在运行时从堆中获得一些内存，而char[size]在编译时提供一些内存，因此变量的大小在代码中是硬编码的