C linked list passing list as argument to the function

**anya** · 08-07-2014

I'm new with linked lists and I have bug that I can not find. I have single linked list filled with numbers which I send as argument to the function search_tnode. If function found number that I'm searching for it returns and in main I can use new list starting with that number. If function does not find the number it returns and in main I have empty list while I want to have original list that I sent as argument. How can I achieve this?

main:

Code:

my_list = search_tnode(my_list,key);

function:

Code:

struct t_node * search_tnode(struct t_node *start_time, unsigned long num){

    struct t_node *p;
    p = start_time;


    while(p != NULL){

        if(p->key == num){
            return p;
        }
        p = p->next;


    }

    printf("Number not found %ld \n",num);
    return start_time;  }

**Salem** · 08-07-2014

> my_list = search_tnode(my_list,key);
The big problem here, is that if you find something, everything before the found node is just leaked away.

Perhaps something like
found_node = search_tnode(my_list,key);

Then if it's important to you
if ( found_node == my_list ) // nothing was found

**vart** · 08-07-2014

Code:

if ( found_node == my_list ) // nothing was found

or first node contains value looked for

**Alpo** · 08-08-2014

If you return NULL when an element is not found, you would have something unique to test against.

**vart** · 08-08-2014

Originally Posted by Alpo

If you return NULL when an element is not found, you would have something unique to test against.

I personally prefer this approach, but the original design also gives a way to test the condition

Code:

found_node = search_tnode(my_list,key);

if ( found_node->key == key )
{
   /* element found */
}
else
{
   /* original list returned, and it does not contain the key */
}

**rcgldr** · 08-08-2014

but this could also be:

Code:

found_node = search_tnode(my_list,key);

if ( found_node->key != NULL )
{
   /* element found */
}
else
{
    found_node = my_list; /* not sure if this is really what OP wants to do */
}

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