#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>


struct stack {
    int  sdata;
	struct stack *next;
} ;

struct stack *Push (struct stack *llist, int data);
struct stack Pop (struct stack ** llist);
void ReleaseStack(struct stack * llist);

int main () {
    struct  stack  *llist = NULL;
    int  data, choice;

    do 
	{
		printf("\nEnter choice (1: Push) (2: Pop) (3: end) : ");
		scanf("%d",&choice);
		while(getchar() != '\n') continue;

		switch (choice) 
		{
			case 1: 
				printf ("Integer to Push onto the stack: ");
				scanf ("%d", &data);
				//clear memory buffer
				while(getchar() != '\n') continue;
				llist = Push(llist,data);
				break;
			case 2: 
				if (llist == NULL) 
				{
					printf ("stack empty!\n");
				}else
				{
					struct stack temp = Pop(&llist);
					printf("%d Popped.\n", temp.sdata);
				}

			case 3: 
				break;

		   default: 
				printf ("Invalid menu choice - try again\n");
				break;
		}

    } while (choice != 3);

    ReleaseStack(llist);

	return 0;
}	



struct stack * Push(struct stack * llist, int data) 
{
	struct stack *newp = NULL;

	if(llist == NULL)
	{
		newp = (struct stack  *) malloc (sizeof (struct stack));
		newp->next = NULL;
		newp->sdata = data;
		llist = newp;
		return llist;
	}else
	{
		newp = (struct stack  *) malloc (sizeof (struct stack));
		newp->sdata = data;
		newp->next = llist;
		return newp;
	}

}

struct stack Pop (struct stack ** llist) 
{
	//holds the return value (data)
	struct stack temp;
	//use to free the head node
	struct stack *freep = *llist; 

	//reposition the head of the stack for post Pop
	if((*llist)->next == NULL) 
	{
		*llist = NULL;
		temp = *freep;
		free(freep);
	}else
	{
		*llist = (*llist)->next;
	
		//get data value
		temp = *freep;

		//free head node
		free(freep);
	}

	return temp;

 }

void ReleaseStack(struct stack * llist) 
{
	while(llist != NULL)
	{
		printf("releasing %d\n", Pop(&llist));
	}
}

#include <stdio.h>
#include <stdlib.h>

struct stack {
    int          data;
    struct stack *next;
};

// push to front
// way simpler than push to rear
void push ( struct stack **head, int val ) {
    struct stack *node = malloc( sizeof(struct stack) );
    node->data = val;
    node->next = *head;
    *head = node;
}
int pop ( struct stack **head ) {
    struct stack *node = *head;
    int result = node->data;
    *head = (*head)->next;
    free( node );
    return result;
}

int main ( ) {
    struct stack *s = NULL;     // its empty
    int i;
    for ( i = 0 ; i < 10 ; i++ ) {
        push( &s, i );
    }
    for ( i = 0 ; i < 10 ; i++ ) {
        printf( "%d\n", pop(&s) );
    }
    printf( "The stack is %sempty\n", s == NULL ? "" : "not " );
    return 0;
}