delete a node at nth position IN C++ - c++

Question

I am having problems deleting from an arbitrary position given in a linked list. I succeeded for the first position and last position of my list but got a runtime error when going for the nth position.
struct node
{
int number;
node *next;
};
struct Box
{
void insertAsFirstElement(node *&head, node *&last,int number);
void insert(node *&head, node *&last,int number);
void remove(node *&head, node *&last);
void showList(node *current);
};
bool isEmpty(node *head) {
return head == NULL;
}
char menu() {
char choice;
cout<<"Menu"<<"1. Add an item.\n"<<"2. Remove an item.\n"<<"3. Show the list.\n"<<"Exit\n";
cin >> choice;
return choice;
}
void insertAsFirstElement(node *&head, node *&last,int number) {
node *temp = new node;
temp->number = number;
temp->next = NULL;
head = temp;
last = temp;
}
void insert(node *&head, node *&last,int number) {
if(isEmpty(head))
insertAsFirstElement(head, last, number);
else {
node *temp = new node;
temp->number = number;
temp->next = NULL;
last->next = temp;
last = temp;
}
}
void remove(node *&head, node *&last,int number) {
cin>>number;
node *temp = new node;
if(isEmpty(head))
cout<< "this list is already empty.\n";
else if (head == last) {
delete head;
head = NULL;
last = NULL;
} else {
for(int i = 0; 1< number-2; i++)
/*node *temp = head;
head = head->next;
delete temp;*/
node *temp = head;
head = head->next;
temp= temp->next;
node* temp2 = temp->next;
temp->next = temp2->next;
delete temp2;
}
}
void showList(node *current) {
if(isEmpty(current))
cout << "The list is empty\n";
else {
cout << "The list contains:\n";
while(current != NULL) {
cout << current->number << endl;
current = current->next;
}
}
}
int main() {
node *head = NULL;
node *last = NULL;
char choice;
int number;
do{
choice = menu();
switch (choice) {
case'1':
cout << "please enter a number: ";
cin >> number;
insert (head,last,number);
break;
case'2':
remove(head,last,number);
break;
case '3':
showList(head);
break;
default:
cout<< "System exit\n";
}
}while (choice !='4');
}

Answer 1

Your loop condition in the removal function is wrong, it's not checking anything affected by the loop, so it would just run forever (or more likely, until it breaks something).
In addition, your remove is not matching its signature. Since you didn't really explain what you want it to do, it's hard to say how to fix it - is number the value you want to remove (what if there are multiple ones?) is it the index to remove? is it a number of elements to remove?
I'll assume it's the second, as it seems like what you were trying to do. In any cases you need to search for that item before deleting it, so instead of -
for(int i = 0; 1< number-2; i++)
try
for(int i = 0; i < number-1; i++)
The 1 was probably a typo, and it's enough to stop one element ahead (the index meaning is up to you, but if the head is 0, then deleting index 2 should run the loop once)
Then, you need to put some brackets around your loop, since right now you're only looping over the first line of code. Move the assignment of temp = head ahead of the loop, you only need to do it once, and loop over
temp= temp->next;
(if that's your only line you don't need brackets, but it's a good habit anyway).
That should bring you to the element ahead of your index. If that's the head, you need some special treatment, but otherwise don't change head, or you'll lose elements you want to keep.
The actual removal looks like it might work, but everytime you dereference next, you need to make sure it's not NULL.