Thread: Help with Linked List

Just started learning Linked List and I am pretty lost. I have started a class but not sure it it is correct. Just need some feed back on if the class is setup right and any additional things about linked list. Every site I have looked at so far has pretty much did and said the same thing and its not helping any. I understand the concept it is just turning it into code.

Code:

#include <iostream>
#include <string>

using namespace std;

#include "swcString.h" //Custom string class

class objList
{
public:
	objList();
	~objList();
	
	objList operator+(objList);

private:
	swcString objName;
	swcString objMaterial;
	int objWeight;
	int objMass;
};

class objNode
{
public:
	objNode();
	objNode(objNode &);
	~objNode();
	void addNewObj();
	void delObj();
	bool emptyObj();
	void traverseObj();
	objList * searchObj();
private:
	objList object;
	objNode *start;
	objNode *next;
	objNode *previos;
	objNode *end;
};

int main (void)
{
	return 0;
}

also when trying to do

Code:

objNode::objNode()
{
}

i get this error:

Code:

ompiling...
main.cpp
Linking...
main.obj : error LNK2001: unresolved external symbol "public: __thiscall objList::objList(void)" (??0objList@@QAE@XZ)
Debug/List.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

List.exe - 2 error(s), 0 warning(s

It is not reconizing my constructor in the class for some reason

Just a couple of design issues/comments. You have an objList class that seems to represent a node of a linked list and an objNode class that seems to represent the list. Just going by the names of these objects I would say the possibility for confusion is very high. Also, it does not seem that your objNode class (actually the list) should have the next and previous pointers, they should be a part of the objList class (actually the nodes). My setup would look like this:

Code:

// The node class contains the pointers to the next and previous nodes
class objNode
{
    swcString objName;
    swcString objMaterial;
    int objWeight;
    int objMass;
    objNode *next;
    objNode *previous;
public:
    ...
};


// The list class should include pointers to the first and last nodes
// It does not contain an actual node element like your original design
// and it also does not contain the next and previous pointers
class objList
{
    objNode *start;
    objNode *end;
public:
    ...
};

Just some suggestions...

As a start:

Code:

#include <iostream>

using namespace std;

#include "swcString.h"

class objNode
{
public:
    swcString objName;
    swcString objMaterial;
    int objWeight;
    int objMass;
    objNode *next;
    objNode *previous;
};

class objList
{
public:
    objList();
    void addObj(swcString, swcString, int, int);

private:
    objNode *start;
    objNode *end;
};

objList::objList() : start(NULL), end(NULL)
{
}

void objList::addObj(swcString nameOfObj, swcString materialOfObj, int weightOfObj, int massOfObj)
{
    objNode *newNode = new objNode;
	
    newNode->objName = nameOfObj;
    newNode->objMaterial = materialOfObj;
    newNode->objWeight = weightOfObj;
    newNode->objMass = massOfObj;

    newNode->next = NULL;
    start = newNode;
}

int main(void)
{
    cout << "Hello World!" << endl;
    return 0;
}

Your addObj function only works for adding the first node and you are also forgetting to set the new node's previous pointer (an approriate objNode constructor could make things like this a bit simpler). You will have to deal with the end pointer as well. Repeated calls to this function would currently result in a memory leak as it stands now.