Linked list copy constructor C++

Tangleman Published at Dev

Tangleman

I am really confused here as to why this copy constructor is not working! I am creating an iter pointer that points to the same ListNode as head, but when I copy stuff from s to it, head and iter are not connected!

In other words when printing head, only the first character is in there, but if I were to iterate through iter, the rest of the list is in there. Why isn't iter and head pointing to the same objects?!

NOTE: This is a linked list being used to implement a class called MyString.

struct ListNode {
    char info;
    ListNode *next;
    ListNode () : info('0'), next(0) {}
    ListNode (char c) : info (c), next(0) {}
};

class MyString {
    private:
    ListNode *head;

    MyString::MyString(const MyString & s) {
        if (s.head == 0)
            head = 0;
        else {
            head = new ListNode (s.head -> info);
            ++NumAllocations;
            ListNode *iter = head;
            for (ListNode *ptr = s.head -> next; ptr != 0; ptr = ptr ->next) {
                iter = iter -> next;
                iter = new ListNode (ptr -> info);
                ++NumAllocations;
            }
        }
    }
}

cdbitesky

You don't appear to be attaching the list to the head anywhere.

Try this.

MyString::MyString( const MyString & s ) {
    if ( s.head == 0)
        head = 0;
    else {
        head = new ListNode (s.head -> info);
        ++ NumAllocations;
        ListNode *iter = head;
        for (ListNode *ptr = s.head -> next; ptr != 0; ptr = ptr ->next) {
            iter -> next = new ListNode (ptr -> info);
            iter = iter -> next;
            ++ NumAllocations;
        }
        printList(head);
    }
}

Notice the attachment of iter->next. You were just creating a new node and doing nothing with it.

Collected from the Internet

Please contact [email protected] to delete if infringement.