Page 81 - DCAP605_ADVANCED_DATA_STRUCTURE_AND_ALGORITHMS

Advanced Data Structure and Algorithms

Notes }
/* pops off the items from the stack */
int pop( )
{
int data ;
if ( pos == -1 )
{
printf ( “\nStack is empty” ) ;
return ( -1 ) ;
}
else
{
data = stack[ pos ] ;
pos-- ;
return ( data ) ;
}
}
2. In this program stack is implemented and maintained using linked list. This
implementation is more sophisticated compared to the one that uses an array, the
added advantage being we can push as many elements as we want. A new node
is created by push( ) (using malloc( )) every time an element is pushed in the stack.
Each node in the linked list contains two members, data holding the data and link
holding the address of the next node. The end of the stack is identified by the node

holding NULL in its link part. The pop( ) function pops out the last element inserted
in the stack and frees the memory allocated to hold it. stack_display( ) displays all
the elements that stack holds. count( ) counts and returns the number of elements
present in the stack.
#include “alloc.h”
struct node
{
int data ;
struct node *link ;
} ;
push ( struct node **, int ) ;
pop ( struct node ** ) ;
main( )
{
struct node *top ; /* top will always point to top of a stack */
int item;
top = NULL ; /* empty stack */
push ( &top, 11 ) ;
push ( &top, 12 ) ;
push ( &top, 13 ) ;
push ( &top, 14 ) ;
push ( &top, 15 ) ;

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