引发链表异常

Question

我是链表的新手，在尝试删除链表的一个节点时遇到此错误。

Exception thrown: Exception thrown: read access violation.
std::_String_alloc<std::_String_base_types<char,std::allocator<char> > >::_Mysize(...) returned 0xDDDDDDF1. occurred

法典：

#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
struct node
{
string song, artist;
node* next;
};
node* add(node *head)
{
string song, artist;
cout << "Enter song name:" << endl;
getline(cin, song);
cout << "Enter artist name:" << endl;
getline(cin, artist);
node *new_ptr = new node;
new_ptr->song = song;
new_ptr->artist = artist;
if (head == nullptr)
{
head = new_ptr;
head->next = nullptr;
}
else
{
node *ptr = head;
while (ptr->next != nullptr)
{
ptr = ptr->next;
}
ptr->next = new_ptr;
ptr->next->next = nullptr;
}
cout << "Song added." << endl;
return head;
}
node* remove(node *head)
{
if (head == nullptr)
{
cout << "There are no songs." << endl;
return head;
}
string song_to_remove;
bool found = false;
cout << "Enter song name to remove:" << endl;
getline(cin, song_to_remove);
if (head->song.compare(song_to_remove) == 0)
{
found = true;
node *temp = head;
head = head->next;
delete temp;
}
else if(head->next != nullptr)
{
node *prev_ptr = head;
node *ptr = head->next;
while (ptr != nullptr)
{
if (ptr->song.compare(song_to_remove) == 0)
{
found = true;
node *temp = ptr;
prev_ptr->next = ptr->next;
delete temp;
}
ptr = ptr->next;
prev_ptr = prev_ptr->next;
}
}
if (!found)
{
cout << "Song not found." << endl;
}
else
{
cout << "Song removed." << endl;
}
return head;
}
void print(node *head)
{
node* ptr = head;
if (ptr == nullptr)
{
cout << "There are no songs added yet." << endl;
}
else
{
while (ptr != nullptr)
{
cout << ptr->song << " by " << ptr->artist << endl;
ptr = ptr->next;
}
}
}
int main()
{
node *head = nullptr;
int option;
while (1)
{
cout << "Choose an option: Add a song (1), remove a song (2), or list all the songs (3)." << endl;
cin >> option;
cin.ignore();
if (!(option == 1 || option == 2 || option == 3))
{
cout << "Must pick either 1, 2, or 3." << endl;
continue;
}
if (option == 1)
{
head = add(head);
}
else if (option == 2)
{
head = remove(head);
}
else if (option == 3)
{
print(head);
}
}
return 0;
}

除了 remove(( 函数之外，我有一切工作，只有当我在链表中有超过 1 个项目并且当我尝试删除第一个节点以外的节点时，它才会出错。

Answer 1

我明白了。删除ptr后我没有break语句，然后试图为ptr分配一些东西。我试图让它工作，以便如果您有多首同名歌曲，它会删除所有歌曲，但该程序不需要那么具体。

node* remove(node *head)
{
if (head == nullptr)
{
cout << "There are no songs." << endl;
return head;
}
string song_to_remove;
bool found = false;
cout << "Enter song name to remove:" << endl;
getline(cin, song_to_remove);
if (head->song == song_to_remove)
{
found = true;
node *temp = head;
head = head->next;
delete temp;
}
else if(head->next != nullptr)
{
node *prev_ptr = head;
node *ptr = head->next;
while (ptr != nullptr)
{
if (ptr->song == song_to_remove)
{
found = true;
prev_ptr->next = ptr->next;
delete ptr;
break;
}
ptr = ptr->next;
prev_ptr = prev_ptr->next;
}
}
if (!found)
{
cout << "Song not found." << endl;
}
else
{
cout << "Song removed." << endl;
}
return head;
}