Thread: deleting for a linked list

for some reason every time i try to delete the plate from the linked list, it returns a zero value. i know that

Code:

 while(crnt->next !=NULL && crnt->next->license != license)
    {
        crnt = crnt->next;
        
    }

is where i am having my problem. it isnt searching for the value and is hitting null to return 0. what am i doing wrong?

Code:

int removecar(struct cars** head, char* license)
{

 struct cars* temp;
 struct cars* crnt;
 
   
   if((*head) == NULL)
        return 0; 
    
    if((*head)->license == license)
    {
        temp = *head;
        (*head) = (*head)->next;
        free(temp);
        return 1;
    }
    crnt = *head;
    while(crnt->next !=NULL && crnt->next->license != license)
    {
        crnt = crnt->next;
        
    }
    if(crnt->next==NULL) //end of list reach and plate not found
    return 0;
    
    temp = crnt->next;
    crnt->next = crnt->next->next;
    free(temp);
    
    return 1;
}

i dont know which to compare.

i tried changing that line to

Code:

while(strcmp(license, crnt->next)==0)

but now its automatically deleting the second character no matter what it is.
as u cant see im not too familiar with strcmp.

And you didn't bother looking it up because why?

But in any event strcmp returns 0 when the two are the same -- so if you want to keep going while they're different you should use !=. And you need to compare license with crnt->next->license -- your compiler should complain about you trying to compare a string with a struct.

i did look it up and i found the same examples that did nothing for me. the compiler did complain but didnt stop me from running the program. in my mind im thinking if crnt = *head and then i need to loop until crnt finds license. when they match delete crnt. what is the difference between me using !=0 and >0?

Code:

    while(strcmp(license, crnt->next->license)!=0){

        crnt = crnt->next;
    }

my program crashes when i try to delete still

Code:

 if((*head) == NULL)
        return 0; 
    
    if((*head)->license == license)
    {
        temp = *head;
        (*head) = (*head)->next;
        free(temp);
        return 1;
    }

this is frees *head if it is the one i am looking for. do i need a strcmp for that also?

Code:

if(crnt->next==NULL) //end of list reach and plate not found
    return 0;

is if the crnt->next is null.

i dont have a dummy node

Originally Posted by vidioholic

Code:

if(crnt->next==NULL) //end of list reach and plate not found
    return 0;

Yes, but if you don't have the check in your while loop you're not going to actually ever stop but run off the end of your list.

ok but why is it deleting the second value in the list every time instead of the one i want?

If you have

Code:

   while(crnt->next != NULL && strcmp(license, crnt->next->license)!=0)

then it isn't. Show new code.

i had:

Code:

    while(crnt->next != NULL && strcmp(license, crnt->next->license)!=0){

        crnt = crnt->next;
    
    
    if(crnt->next==NULL) //end of list reach and plate not found
    return 0;

then i changed it to what you said. now its not deleting anything... do you want me to post me entire code? maybe there is an issue somewhere else in my code?

Where did your closing curly brace go? Yes, show the whole thing then.