/* Program implements linked list as a stack. */

/*   Program implements linked list as a stack. */
#include <stdio.h>
#include <conio.h>
#include <alloc.h>
/* structure containing data part and linkpart */
struct node
{
 int data ;
 struct node *link ;
} ;
void push ( struct node **, int ) ;
int pop ( struct node ** ) ;
void delstack ( struct node ** ) ;
void main( )
{
 struct node *s = NULL ;
 int i ;
 clrscr( ) ;
 push ( &s, 14 ) ;
 push ( &s, -3 ) ;
 push ( &s, 18 ) ;
 push ( &s, 29 ) ;
 push ( &s, 31 ) ;
 push ( &s, 16 ) ;
 i = pop ( &s ) ;
 printf ( "\nItem popped: %d", i ) ;
 i = pop ( &s ) ;
  printf ( "\nItem popped: %d", i ) ;
 i = pop ( &s ) ;
 printf ( "\nItem popped: %d", i ) ;
 delstack ( &s ) ;
 getch( ) ;
}
/* adds a new node to the stack as linked list */
void push ( struct node **top, int item )
{
 struct node *temp ;
 temp = ( struct node * ) malloc ( sizeof ( struct node ) ) ;
 if ( temp == NULL )
  printf ( "\nStack is full." ) ;
 temp -> data = item ;
 temp -> link = *top ;
 *top = temp ;
}
/* pops an element from the stack */
int pop ( struct node **top )
{
 struct node *temp ;
 int item ;
 if ( *top == NULL )
 {
  printf ( "\nStack is empty." ) ;
  return NULL ;
 }
 temp = *top ;
 item = temp -> data ;
 *top = ( *top ) -> link ;
 free ( temp ) ;
 return item ;
}
/* deallocates memory */
void delstack ( struct node **top )
{
 struct node *temp ;
 if ( *top == NULL )
  return ;
 while ( *top != NULL )
 {
  temp = *top ;
  *top = ( *top ) -> link ;
  free ( temp ) ;
 }
}