Hello, I've been struggling to implmenent a 2 way link list. The code runs but when I enter the 2nd element into the list I get a segmentation fault......I cant find my error could anyone take a look?

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#include <iostream>

using namespace std;

typedef struct record
{
int num;
record *next;
record *previous;

}NODE;

typedef NODE *nodeptr;

void frontinsert(nodeptr &, int);
void printlist(nodeptr &);
void deleteitem(nodeptr &, int);
void searchitem(nodeptr &, int);

int main()
{
int item, choice;
nodeptr head = NULL;


cout << "Please select an option: \n";
cout << "Insert select 1\nDelete select 2\nSearch select 3\nQuit select 4\n";
cin >> choice;


while (choice != 4)
{
switch(choice)
{
case 1: cout << "Enter a number to insert into the list: \n";
cin >> item;

frontinsert(head, item);

cout << "The list is: \n";

printlist(head);
break;

case 2: if(head != NULL)

{
cout << "Please enter the item you wish to delete:\n";
cin >> item;

deleteitem(head, item);

if (head != NULL)
{
cout << "The list is: \n";

printlist(head);
}

else
cout << "CANNOT delete, the list is empty\n" << endl;
}
break;

case 3: if(head != NULL )
{
cout << "Please enter the item you wish to search for:\n";
cin >> item;

searchitem(head, item);
}
else
cout << "CANNOT search, the list is empty\n" << endl;
break;

default: cout << "Invalid selection. Please try again\n" << endl;
}

cout << "Please select an option: \n";
cout << "Insert select 1\nDelete select 2\nSearch select 3\nQuit select 4\n";
cin >> choice;

}

free(head);
return 0;
}

void frontinsert(nodeptr &h, int d)
{
nodeptr p = new NODE;
nodeptr q;
nodeptr r;

if (p == NULL)
cout << "No memory is left" << endl;
else
{
p->num = d;
if (h == NULL )
{
h = p;
p->previous = NULL;
p->next = NULL;
}

else if (d <= h->num)
{
r=h;
p->next = h;
r->previous = p;
h = p;
p->previous = NULL;
}
else
{
r = h;
while(r != NULL && r->num < d)
{
q = r;
r = r->next;
}

if(r == NULL)
{
p->previous = q;
q->next = p;
p->next = NULL;
}
else
{
p->next = r;
p->previous = q;
q->next = p;
r->previous = p;
}
}
}
}



void deleteitem(nodeptr &h, int d)
{
nodeptr p;
nodeptr q;

if (h != NULL)
{
if (h->num == d && h->next != NULL)
{

h = h->next;
p = h;
p->previous = NULL;
}

else if (h->num == d && h->next != NULL)

h = NULL;

else
{
p = h;
q = h->next;
}

while (q != NULL && q->num < d)
{
p = q;
q = q->next;
}


if (q->num == d && q->next == NULL)
{
q = q->next;
q->previous = p;
p->next =q;
}

else if (q->num == d && q->next != NULL)

p->next = NULL;

else
cout << "Item is not in the list\n" << endl;

}

}



void searchitem(nodeptr &h, int d)
{
nodeptr q;

q = h;

while(q != NULL && q-> num != d)
q = q->next;

if (q != NULL && q->num == d)
cout << "Item is in the list\n";
else
cout << "Item is not in the list\n";

}

void printlist(nodeptr & h)
{
nodeptr currptr = h;

while(currptr != NULL)
{
cout << currptr->num << endl;
currptr = currptr->next;
}
}
[/php]

I can't seem to figure out what your insert algorithm is. Can you explain it? I spent about 5 minutes looking at it and it's all a jumble.

A few comments:
--Make liberal use of comments. // for single line comments /* */ for multi-line comments.
--Use good variable names. That means names that tell the reader of the code what you're doing. (Try temporary, current, previous, or temp, cur, prev if you're lazy.)
--Don't assume pointers are NULL. Initialize them when you declare them.

If you use GCC to do your compilation, I'm sure there's a program installed called gdb. It's a wonderful program (IMO) to use once you learn how. It's really really useful for debugging C++ because it will let you know WHERE the program failed and at your request will display a variable's contents before it fails. You need to compile with debug points in: