Linked List Questions

LoSTimberWolf · Post by **LoSTimberWolf** » Sat Mar 29, 2003 11:15 pm

My Program 7 for class is dealing with linked lists. Each node contians an object and a pointer. I must be able to output the numbers in the object in each node, but I currently can not. I also am getting an error that does not make sense, " 'cout' : ambiguous symbol". The next problem is how do you reverse a linked list? I know it takes a temp list to copy into but I still can't figure out the proper configuration of loops and limits for those loops. Any information would be helpful. Thanks in advance. -LoS-TimberWolf{FF} Vehicle Specilist

Scorch · Post by **Scorch** » Sun Mar 30, 2003 3:53 am

Assuming you have... There are many ways of setting up a link list, from the sound of it here is what you have (or somthing similar, perhaps a LL class itself, but I don't wantto have to write everything now <img src=http://www.ezboard.com/images/emoticons/smile.gif ALT=":)"> ) Anyways <pre> class Node {Node *next;int number;};Node::Node(){next=NULL;}in main you would havemain(){int x;Node *top, *curr, *rev, *revPrev;I can't remember if you need *Node or just Node for the new, sorry <img src=http://www.ezboard.com/images/emoticons/frown.gif ALT=":("> top = new Node; // Top is now the top of your linked listrev = new Node;revPrev = NULL;curr = top; // I do it this way (use a seperate pointer) that way I reduce the risk of breaking the list.while (condition != met){cin>> curr->number; // or curr.number forget which try one if it don't work try other.curr->next = new Node;curr = curr->next; // moves to new thing, although in this// case you would alwayshave an empty node at the end of //your list, no biggie, but you might want to play around with //what I have to get rid of it.}Now to reverse it, assuming you always have the last one pointing at NULL.curr = top;while (curr != null){rev->next = revPrev;revPrev = rev;rev.number = curr.number;rev= new Node;curr = curr->next;}</pre> *edited for line length.* Edited by: <A HREF=http://pub141.ezboard.com/bxmenclan.sho ... ambit>XMEN Gambit</A>  <IMG SRC="http://www.xmenclan.org/images/x.gif" BORDER=0> at: 4/2/03 10:04:25 pm

Post by **XMEN Gambit** » Sun Mar 30, 2003 1:24 pm

Scorch's answer is pretty good - a few syntax errors but that what the compiler's first pass is for, right? This might be "cheating" a bit, but you COULD build yourself a doubly-linked list, where each node has a pointer to the previous node AND to the next node. Then you'd only need a pointer to the tail node to traverse the list in reverse order. I love linked lists. Learning about them was one of those moments in computer science when the lightbulb clicked on and I went "WOW!". <img src=http://www.ezboard.com/images/emoticons/glasses.gif ALT="8)"> <img src="http://www.xmenclan.org/xmengambit.gif"/> XMEN member Card-carrying DTM OKL Fish-napper Though a program be but three lines long, someday it will have to be maintained.  The Tao of Programming

LoSTimberWolf · Post by **LoSTimberWolf** » Wed Apr 02, 2003 6:35 pm

Ok, my only listed compiling error is an INTERNAL COMPILER ERROR, I so am trecking along to my thursday deadline. -LoS-TimberWolf{FF} Vehicle SpecilistEdited by: <A HREF=http://pub141.ezboard.com/bxmenclan.sho ... berWolf</A> at: 4/2/03 8:14:41 pm

Post by **XMEN Gambit** » Wed Apr 02, 2003 8:30 pm

Um, are you trying to compile Scorch's code, or did you write some yourself? Do you have a line number? <img src="http://www.xmenclan.org/xmengambit.gif"/> XMEN member Card-carrying DTM OKL Fish-napper Though a program be but three lines long, someday it will have to be maintained.  The Tao of Programming

LoSTimberWolf · Post by **LoSTimberWolf** » Wed Apr 02, 2003 8:52 pm

I have written my own code based off of the functions that already exist in the object I am modifing. It is having a problem witht he cout statement still. This function came with the object. Here is the function: void RectangleList::displayList(void) { &nbsp &nbsp &nbsp &nbsp ListNode *nodePtr; &nbsp &nbsp &nbsp &nbsp nodePtr = head; &nbsp &nbsp &nbsp &nbsp while (nodePtr) &nbsp &nbsp &nbsp &nbsp { &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp cout << "Width: " << nodePtr->value.getWidth << ", "; &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp cout << "Length: " << nodePtr->value.getLength << ", "; &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp cout << "Area: " << nodePtr->value.getArea << endl; &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp nodePtr = nodePtr->next; &nbsp &nbsp &nbsp &nbsp } } -LoS-TimberWolf{FF} Vehicle Specilist

XMEN Ashaman DTM · Post by **XMEN Ashaman DTM** » Wed Apr 02, 2003 9:01 pm

This might sound dumb, but aren't your "<<" supposed to point the other way in an assignment? (">>" instead of "<<") <img src=http://www.xmenclan.org/avatars/ashaman2.jpg width=150 align=left> <left><a href=http://www.dragontalonmercs.com>Dragon Talon Mercenary</a> <a href=http://www.xmenclan.org>Member of the XMEN</a> Have a Nice Day! </left>

XMEN Ashaman DTM · Post by **XMEN Ashaman DTM** » Wed Apr 02, 2003 9:02 pm

For the 'cout' function, I mean. cout>>blahblah <img src=http://www.xmenclan.org/avatars/ashaman2.jpg width=150 align=left> <left><a href=http://www.dragontalonmercs.com>Dragon Talon Mercenary</a> <a href=http://www.xmenclan.org>Member of the XMEN</a> Have a Nice Day! </left>

Post by **XMEN Gambit** » Wed Apr 02, 2003 10:08 pm

Well, in this particular case I think I see your problem. What is "value.getWidth" ? Is that a public member variable? Or is it a method? If it is the latter, which it most likely is, then you need to indicate that it is a method by adding a set of "()". The compiler chokes on it because cout doesn't have a clue what to do with a function pointer. Learning to debug is the single most useful universal programming skill. (Asha, cin and cout are kind of weird beasties. Hardly ever used in a production app, they're more for debugging. The data flows in the direction of the arrows, and you want the data going out to the console.) <img src="http://www.xmenclan.org/xmengambit.gif"/> XMEN member Card-carrying DTM OKL Fish-napper Though a program be but three lines long, someday it will have to be maintained.  The Tao of ProgrammingEdited by: <A HREF=http://pub141.ezboard.com/bxmenclan.sho ... ambit>XMEN Gambit</A>  <IMG SRC="http://www.xmenclan.org/images/x.gif" BORDER=0> at: 4/2/03 10:10:38 pm

XMEN Ashaman DTM · Post by **XMEN Ashaman DTM** » Thu Apr 03, 2003 12:03 am

Ah! That's odd. Though I don't think I've used either function more than once. Heh. <img src=http://www.xmenclan.org/avatars/ashaman2.jpg width=150 align=left> <left><a href=http://www.dragontalonmercs.com>Dragon Talon Mercenary</a> <a href=http://www.xmenclan.org>Member of the XMEN</a> Have a Nice Day! </left>

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