Data Structure and Algorithm

#include <iostream.h>
#include <conio.h>
#include <stdlib.h>

class stack
{
private:
  int data;
  stack *next;
public:
  stack() {next = NULL;}
  friend void create(); //function to create a node
  friend void push(stack *&,int); //function to push item on stack
  friend stack* pop(stack *&); //function to delete item from stack
  int getdata() {return data;} //function to return the data of particular node
  ~stack() {delete next;}
};

stack *New,*head,*top;
void create()
{
New = new stack;
New -> next = NULL;
}

void push (stack *&nd,int Item)
{
if(nd == NULL) //if first node
  {
   nd = new stack; //create first node
   nd -> next = NULL; //initialize next pointer field
   nd -> data = Item; //push item
   head = nd; //update head
   top = nd; //update top
   return;
  }

create(); //create a node
New -> data = Item; //push item
top -> next = New; //add to list
top = New; //update top
}

stack* pop (stack *&nd)
{
if(nd == NULL) //if stack is empty
  {
   cout << "\nStack Underflow";
   cout << "\nPress any key to halt...\n";
   getch();
   exit(0);
  }

stack *deleted;
if(top == nd) //if only one node
  {
   deleted = nd;
   top = NULL;
   nd = NULL;
   return deleted;
  }

deleted = top;
stack *temp = head;
while(temp -> next != top) //goto secondlast node
  temp = temp -> next;

temp -> next = NULL;
top = temp; //update top
return deleted;
}

int main()
{
stack *s = NULL;
for(int i = 1;i <= 5;i++) //push 5 items to list
  push(s,5*i);

for(int i = 1;i <= 5;i++)
  {
   stack *result = pop(s); //pop items and
   cout << result -> getdata() << ' '; //display
  }

getch();
return 0;
}

OUTPUT

25 20 15 10 5

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