link list build: memory access denied
hi guys. I created a simple code to build linked list.
following are the various files
Header file
Code:
class ListBuild
{
private:
struct node {
int d;
node * next; // next pointer
};
typedef node * list; // list == node*
list head ,tail,prev; // pointer to head and tail static member
static int sz; // current size of list,static member
public:
ListBuild () ; // default constructor
ListBuild (const ListBuild & Lst); // copy constructor
~ListBuild() ; // default destructor
int findlength()const; // find size
void insert(int newitem); // add node
void findpr()const; // previous pointer that tail
void remove(); // remove node
void print(); // print list
};
Implementation file
Code:
#include <iostream>
#include "Link_list_build.h"
using namespace std;
int ListBuild::sz=0;
ListBuild ::ListBuild() // default constructor
{
head=0; //Null pointer
tail=0;
prev=0;
}
ListBuild ::ListBuild(const ListBuild& lst) // copy constructor
{
}
ListBuild ::~ListBuild() // default destructor
{
remove() ; // call func to remove node memory
}
int ListBuild::findlength()const // determine current size of list
{
return sz;
}
void ListBuild ::insert(int newitem) // add item at start or inbetween
{
//int newlngth= findlength()+1;
// creates new node structure and returns pointer to it
list newnode = new node ;
if( newnode ==NULL)
cout<< " could not allocate memory";
else
{
sz= findlength();
newnode->d = newitem;
newnode->next=NULL;
if (sz==0) // allocate first node
{
head= newnode;
tail=head;
}
else // allocate rest nodes
{
tail->next = newnode;
tail=newnode;
}
sz++;
} // end of if( newnode ==NULL)
}
void ListBuild::findpr()const
{
if (sz==0)
cout<< "already empty list"<<endl;
else if(sz==1)
{ } // do nothing
else
{
list prev = head;
for (int i=0;i<sz-1;i++)
{
prev= prev->next;
}
}
}
void ListBuild ::remove() // remove item
{
--sz;
if (sz==0)
cout<< "already empty list"<<endl;
else if (sz==1) // delete first node
{
delete tail;
tail=NULL;
}
else // delete rest nodes
{
list curr;
curr= prev->next; // now points to node be deleted
prev->next = curr->next;
curr=NULL;
delete curr;
}
}
void ListBuild ::print()
{
list temp=NULL;
temp=head; // dont want to change head pointer, so create another temp //pointer
for (int i=0;i<sz;i++)
{
cout<< temp->d<<'\t';
temp=temp->next;
}
}
and the user file
Code:
#include <iostream>
#include "Link_list_build.h"
using namespace std;
int main()
{
ListBuild a,b,c ;
a.insert(10); // insert at start
a.print();
b.insert(20); // insert at end and build list
b.print();
c.insert(30);
c.print();
}
.
the code compiles and allocates first node. but, as i pass second node data, it reaces
Quote:
tail->next = newnode;
within "insert" function and gives memory access violation.
any ideas why? I do not see why it should.
I also had other question,while copying code here, how do i copy line numbers ?
thanks
sedy
