help with adding item to linked list in C

This is a discussion on help with adding item to linked list in C within the C Programming forums, part of the General Programming Boards category; Code: shift(buffer,4); tmp_buffer1 = malloc(strlen(buffer) * sizeof(char)); get_first_num(buffer,tmp_buffer1); check = strlen(tmp_buffer1)+1; shift(buffer,check); check=0; item_num=0; tmp_item_list=item_list; while(tmp_item_list) { if (strcmp(tmp_item_list->number,tmp_buffer1)==0 && ...

  1. #1
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    Angry help with adding item to linked list in C

    Code:
    shift(buffer,4); 
    tmp_buffer1 = malloc(strlen(buffer) * sizeof(char)); 
    get_first_num(buffer,tmp_buffer1);
    check = strlen(tmp_buffer1)+1;
    shift(buffer,check); 
    check=0; item_num=0; tmp_item_list=item_list; 
    while(tmp_item_list) {
    	if (strcmp(tmp_item_list->number,tmp_buffer1)==0 && atoi(buffer)>atoi(tmp_item_list->current_price)) { 
    		tmp_buffer2 = malloc(strlen(buffer) * sizeof(char)); strcpy(tmp_buffer2, tmp_item_list->name);
    		tmp_buffer3 = malloc(strlen(buffer) * sizeof(char)); strcpy(tmp_buffer3, tmp_item_list->number);
    		tmp_buffer4 = malloc(strlen(buffer) * sizeof(char)); strcpy(tmp_buffer4, buffer);
    		item_list = add_item(tmp_buffer2, tmp_buffer3, tmp_buffer4, "DUDE", item_list);
    		remove_item(item_list, item_num+1, 0);	
    		send_message(i, "OK"); check=1; break; 
    	}
    	tmp_item_list=tmp_item_list->next; item_num++;
    }
    if (check==0) send_message(i, "NO");
    What i am trying to do is edit the strings of a node in a linked list.
    The way i am doing it is, first finding the node in a copied version of the linked list (which i don't think i did right), then making a new node and coping the details to the new node, and adding my own string, then add the new node to the front of the list, then delete the found node from the list. Right now this isn't working as the list isn't circular, just linear (supposed to be linear and stops) which stops somewhere. After doing this, the list ends up repeated like 2 times... which is bad... what is wrong here?
    Last edited by omega666; 04-04-2011 at 07:41 PM.

  2. #2
    ATH0 quzah's Avatar
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    If it's not circular, all you should have to do is:
    Code:
    for( node = firstnode; node != NULL; node = node->next )
    {
        ...do whatever it is you are trying to do...
    }
    If it is circular, then you just need to keep track of where you started, and if you are back there again, stop looking.


    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
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    i changed it to
    Code:
    						item *node = NULL;
    						for(node = item_list; node != NULL; node = node->next) {
    							if (strcmp(node->number,tmp_buffer1)==0 && atoi(buffer)>atoi(node->current_price)) { 
    								node->high_bid="dude";
    								check=1;
    								break;
    							}
    						}
    but still a problem, since it didn't make a copy, the original list called item_list is now null after this for loop...


    does this have to be in a function? btw, i have it in my main function...

  4. #4
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    i changed it again to
    Code:
    						check=0;
    						item *ptr = NULL;
    						for(ptr = item_list; ptr != NULL; ptr = ptr->next) {
    							if (strcmp(tmp_buffer1, ptr->number)==0) { 
    								if (atoi(buffer)>atoi(ptr->current_price)) { 
    									char *tmp_buffer = malloc(strlen(buffer) * sizeof(char)); strcpy(tmp_buffer, buffer);
    									ptr->current_price=tmp_buffer;
    									ptr->high_bid="dude";
    									send_message(i, "OK");
    									check=1;
    								}
    							}
    						}

    and its still copying a copy of the list to the end, making it repeat twice, i dont see where the pointers are going wrong...

  5. #5
    Banned
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    Presently you have two threads running for essentially the same code...

    Please pick one or the other and stick to it.

    Thanks.

  6. #6
    Registered User
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    ok delete this thread then, since the other is fine

  7. #7
    Registered User whiteflags's Avatar
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    The way i am doing it is, first finding the node in a copied version of the linked list (which i don't think i did right),
    I'd do that right before moving on.

    then making a new node and coping the details to the new node, and adding my own string, then add the new node to the front of the list, then delete the found node from the list.
    I can understand wanting to copy a linked list to preserve the original list, but is there a reason you don't simply change the node's data after you find it?

    After you've found the node you want to edit, do this:

    strcpy( foundnode->highbid, "dude" );

    You should be done after that.

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