CODEWITHSUNDEEP
visual-c++linked-listdeep-copy
Claud
Claud

Reputation: 1075

Deep copy of linked list c++

I'm trying to make a deep copy for my simple linked list that I've made. I'm trying to get the basics of it and any help would be appreciated. I just want to take the first value in the old list and deep copy it to the new list.

#include<iostream>
using namespace std;

struct listrec
{
char        value;
struct listrec    *next;
};


void deepcopy(listrec *old_linked_list,  listrec *new_linked_list)
{

while(old_linked_list != NULL)
{
    new_linked_list->value = old_linked_list->value;
    new_linked_list->next = old_linked_list->next;
    old_linked_list = old_linked_list->next;
    new_linked_list = new_linked_list->next;
}
}



int main()
{
listrec x1,x2,x3;
listrec *head_old, *head_new=NULL;

x1.value = 'a';
x1.next = &x2;

x2.value = 'c';
x2.next = &x3;

x3.value = 'w';
x3.next = NULL;

head_old = &x1;
head_new = head_old;

deepcopy(head_old, head_new);

//print old list
cout<<"Old List: "<<endl;
while(head_old != NULL)
{
    cout<<head_old->value<<endl;
    head_old= head_old->next;
}

cout<<endl;

//print copied list
cout<<"Copied list: "<<endl;
while(head_new != NULL)
{
    cout<<head_new->value<<endl;
    head_new= head_new->next;
}


system("pause");
return 0;
}

The program works and it makes a copy but I just want to make sure its a deep copy and not a shallow copy. What do you guys think?

Upvotes: 1

Views: 978

Answers (1)

Roman Byshko
Roman Byshko

Reputation: 9032

You are passing head_new which is NULL to deepcopy. Then you try to deference (access) it. This gives you segmentation fault (error), since you cannot deference a NULL pointer. (You cannot access nothing, because your pointer points to nothing.)

To correct your code must allocate memory for head_new in main and for each next node in in deepcopy. Also you should move on your new_linked_list, as you assign all the time to the same node.

Upvotes: 1

Related Questions