Linked List Exception Thrown - c++

Question

I am new with linked lists and I am getting this error when trying to remove one of the nodes of a linked list.
Exception thrown: Exception thrown: read access violation.
std::_String_alloc<std::_String_base_types<char,std::allocator<char> > >::_Mysize(...) returned 0xDDDDDDF1. occurred
Code:
#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;
}
I have everything working besides the remove() function, and it only errors when I have more than 1 item in the linked list and when I try to remove a node besides the first one.

Answer 1

I got it. I didn't have a break statement after deleting ptr and then was trying to assign something to ptr. I was trying to make it work so that if you had multiple songs with the same name it would delete all of them, but the program doesn't need to be that specific.
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;
}