Thread: Linked list

Hi,

I was following the linked list tutorial on this site. I have the code here, but I am not sure if I am doing it right. Could someone tell me if I am on the right track, or is there a way I could do it better ?

Thanks in advance.

Code:

#include <cstdio>
#include <iostream>

using namespace std;

struct Node {
    int x;
    Node *next;
};

void AddNode(Node *node, int value)
{
    if(node != NULL)
    {
        while(node->next != NULL)
        {
            node = node->next;
        }
    }
    
    node->next = new Node;
    node = node->next;
    node->next = NULL;
    node->x = value;
}    
    
void PrintValue(Node *node)
{
    do 
    {
        cout << node->x << endl;
        node = node->next;
    }while(node != NULL);
}
        
int main()
{
    Node *root = new Node;
    root->next = NULL;
    root->x = 5;
        
    AddNode(root, 10);
    AddNode(root, 30);
    AddNode(root, 50);
 
    PrintValue(root);   
    
    getchar();
    return 0;
}

I'd suggest you post to the C++ forum.

In the first call of AddNode you will loose the pointer
to your root.
You should use a const Node in AddNode param
and make a copy of it.
and then iterate until the end.

Code:

void AddNode(const Node *root, int value)
{
    if(root != NULL)
    {
        Node* node = root;
        while(node->next != NULL)
        {
            node = node->next;
        }
    }
    
    node->next = new Node;
    node = node->next;
    node->next = NULL;
    node->x = value;
}

Do this in PrintValue also else you will have
memory leaks and you will never get back to
your root node !!!!

Ciao Ephraim

Ok, no problem, I will post it there, but I don't see a lot of C++ in it except for new and cout.

Originally posted by c99
I'd suggest you post to the C++ forum.

Why ?? I thought structs are also available in C!!??

Or what problem do you have with this code?

[EDIT]Ohh jep new, cout and using namespace bla are c++, but the main thing
is the linked list and this can also be programmed with c[/edit]

Ciao Ephraim

Originally posted by Ephraim
In the second call of AddNode you will loose the pointer
to your root.
You should use a const Node in AddNode param
and make a copy of it.
and then iterate until the end.

Code:

void AddNode(const Node *root, int value)
{
    if(root != NULL)
    {
        Node* node = root;
        while(node->next != NULL)
        {
            node = node->next;
        }
    }
    
    node->next = new Node;
    node = node->next;
    node->next = NULL;
    node->x = value;
}

Do this in PrintValue also else you will have
memory leaks and you will never get back to
your root node !!!!

Ciao Ephraim

If I make it const Node *root, then I wouldn't be able to do

Code:

Node* node = root;

Secondly I dont get it, how would I add data if I make a variable constant like

const Node *node = root; ?

Thanks

Originally posted by gautamn
Ok, no problem, I will post it there, but I don't see a lot of C++ in it except...

And that's all you needed to see. If any of it is C++, then it can't complie on a C compiler, now can it?

You should pass a pointer to a pointer (for the root node) to the add function, so you can actually update what it points at.

Quazh.

This is the basic idea:

Code:

 struct Node 
{
 struct Node * next;
 int value;
};


 struct Node * AllocNode(int initial)
{
 struct Node * node = (Node*)malloc(sizeof(struct Node));
 
     if(node != NULL)
    { 
     node->next = 0;
     node->value = initial;
    }
    
 return node;    
}


 void DestroyList(struct Node ** root)
{
 struct Node * next, * prev = *root;
 
     while(prev != NULL)
    {
     next = prev->next;
     free(prev);
     prev = next;
    } 
    
 *root = 0;   
}


 struct Node * AddNode(struct Node ** root, int value)
{
 struct Node * next = *root;

 struct Node * node = AllocNode(value);
 
     if(*root != NULL)
    {
         while(next->next != NULL)
        {
         next = next->next;
        }
        
     next->next = node;     
    } 
     else
    {
     *root = node;
    }  
    
 return node;
}


 void PrintList(struct Node * root)
{
 struct Node * next = root;
 
     while(next != NULL)
    {
     printf("%d\n", next->value);
     
     next = next->next;
    } 
}



 int main()
{
 struct Node * root = NULL;
 
 AddNode(&root, 10);
 AddNode(&root, 9);
 AddNode(&root, 8);
 AddNode(&root, 7);
 PrintList(root);
 DestroyList(&root);

 return 0;
}