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linked list rep. of stack

Posted on 1998-11-18
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Last Modified: 2012-05-04
What is the code for a linked list rep. of a stack in C++.
Lost my code. need it though.
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Question by:krn
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by:alexo
ID: 1254377
This question sounds suspiciously like homework.  In that case t will be unethical for us to write it for you.  However, we can help with *specific* problems.

To get you started:

A stack usually implements two operations, PUSH - which pushes an item on the stack and POP - which returns the topmost item and removes it from the stack (sometimes the query and removal are split into two distinct operations).

An implementation using a linked-list can either add and remove items from the beginning of the list (if the list supports such operations) or keep a pointer to the last item.

Case #1:
  PUSH(item) - Add the new item to the beginning of the list.
  POP() - Return the first item and remove it from the list.

Case #2:
  PUSH(item) - Add the new item to the end of the list and update the pointer.
  POP() - Return the item pointed to (last item) and remove it from the list.

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Author Comment

by:krn
ID: 1254378
Well in that case, I must decrease the points.
I will, on the pother hand, ask more questions about the problem as they arise.
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Accepted Solution

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baprebap earned 200 total points
ID: 1254379
i will just write the POP and PUSH for you.
define a struvture as follows

struct  stacktype
{
 char *info;
 struct stacktype *link;;
};

allocate memory dynamically using the malloc() command.
firstnode is initialised to NULL in the main().the fn is invoked as
firstnode=push(firstnode,"KLJA');
pop is also called as above except that it does not take the char * field.
you may use typedef for struct stacktype * .it will be a better programming style.
pop may also be used to return the element deleted..to do so change the return type


struct stacktype *push(struct stacktype *firstnode,char *info)
{
 struct stacktype *newnode;
 newnode=(struct stacktype *)malloc(sizeof(stacktype));
 if (newnode==NULL) return(firstnode);
 strcpy(newnode->info,info);
 if (firstnode==NULL)
 {
  newnode->link=NULL:
  return(newnode);
 }
 else
 {
  newnode->link=firstnode;
  return(newnode);
 }
}

struct stacktype *pop(struct stacktype * firstnode)
{
 struct stacktype *save=firstnode;
 firstnode=firstnode->link;
 cout << "The element popped is ;" << save->info;
 free(save);
 return(firstnode);
}



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Author Comment

by:krn
ID: 1254380
Thanks
That is really what I was having problems with.
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Expert Comment

by:alexo
ID: 1254381
>> Well in that case, I must decrease the points.
You cannot decrease points for a question.  However, you can delete a question that has no pending or rejected answers and submit another one (that is the reason I gave a comment and not an "answer").

This is just for reference since I see you got your answer.
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