Implements linked list as a stack.

C: 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 ) ;
    }
}