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Adding node to end of linked list

NostawTtam (16)
I have a header with inline implementation and I have a node header that returns all the values I need. I know my node header is correct, but when I run my program I am getting a runtime error in my push_back function. This function is supposed to be adding a node to the end of the list. Could anyone tell me what I am doing wrong?
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#ifndef LLIST_H
#define LLIST_H
#include "node.h"
#include <string>
#include <iostream>
using namespace std;


class LList{
private:	
	
	typedef string valueType;

	Node* head;
	Node* tail;

public:
	LList();
	LList(const LList&);
	~LList();
	void push_front(const valueType&);
	void push_back(const valueType&);
	void delete_list(Node*&); 
	void operator=(const LList&);
	friend ostream& operator<<(ostream&, const LList&);
	void list_copy(const LList&);

};

inline LList::LList()
{
	head = NULL;
	tail = NULL;
}

inline LList::LList(const LList& source)
{
	//Node* tail_ptr;
	list_copy(source);
}

inline LList::~LList()
{
	cout << endl << "The destructor has been called.\n";
	delete_list(head);
}

inline void LList::delete_list(Node* &head_ptr)
{
	Node* remove_ptr;

	while (head_ptr != NULL)
	{
		remove_ptr = head_ptr;
		head_ptr = head_ptr->next();
		delete remove_ptr;
	}
	
}

inline void LList::push_back(const valueType& entry)
{
	Node* insert_ptr;
	Node* previous_ptr;
	previous_ptr = NULL;
	
	insert_ptr = new Node(entry);
	insert_ptr->str(entry);
	insert_ptr->next(previous_ptr->next());
	previous_ptr->next(insert_ptr);

}

inline void LList::push_front(const valueType& entry)
{
	head = new Node(entry);
}

inline void LList::list_copy(const LList& source)
{
	//Node* temp;
	//temp = new Node;
	///*head_ptr = NULL;
	//tail_ptr = NULL;*/

	//if(source_ptr == NULL)
	//{
	//return;
	//}
	////push_front(source_ptr->str());
	//tail_ptr = head_ptr;

	//source_ptr = source_ptr->next();
	//while(source_ptr != NULL)
	//{
	//	push_back(source_ptr->str());
	//	tail_ptr = tail_ptr->next();
	//	source_ptr = source_ptr->next();
	//}
}

inline void LList::operator=(const LList& source)
{
//	Node* tail_ptr;

	if(this == &source)
	{
		return;
	}

	list_copy(source);

	delete_list(head);

}

inline ostream& operator<<(ostream& out, const LList& L)
{
	Node* p;
	
	for(p = L.head; p != NULL; p=p->next())
	{
		out << p->str()<<endl;
		out << endl;
		
	}
	return out;
}

#endif
ResidentBiscuit (4459)
What is node::str()? Your push_back method doesn't look right at all. You need to traverse until your pointer (current position) node has a next pointer of null, signalling it's the last in line. Then create a new node, and set the current.next = newNode.

EDIT:
node::str is your data. Anyways, you're also setting previous_ptr to null, then trying to dereference it. That's a pretty big issue. Definitely rework your logic here.
Last edited on
NostawTtam (16)
node::str() returns the string, and the line before tht sets the string into the node and sets next to NULL
NostawTtam (16)
Okay, tell me if this sounds right. If I have a head and tail pointer and I test them and they are equal to NULL then I can just add the node else I can iterate through the node till I get to tail->NULL and add the node there?
cire (8284)
If you have a data member tail that points to the last node in the list, why would you need to iterate through the list?
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