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

struct Node
{
    char *data;
    struct Node *link;
};
struct Node *top;

void push(char *data)
{
    struct Node *temp;
    temp = (struct Node *)malloc(sizeof(struct Node));
    if (!temp)
    {
        printf("\nHeap Overflow");
        abort();
    }
    temp->data = _strdup(data);
    temp->link = top;
    top = temp;
}

int isEmpty()
{
    return top == NULL;
}

char *peek()
{

    if (!isEmpty(top))
        return top->data;
    else
        abort();
}


void pop()
{
    struct Node *temp;


    if (top == NULL)
    {
        //printf("\nStack Underflow");
        abort();
    }
    else
    {
        // top assign into temp
        temp = top;

        // assign second node to top
        top = top->link;

        // destroy connection between first and second
        temp->link = NULL;

        // release memory of top node
        free(temp);
    }
}

void display() // remove at the beginning
{
    struct Node *temp;

    // check for stack underflow
    if (top == NULL)
    {
        //printf("\nStack Underflow");
        abort();
    }
    else
    {
        temp = top;
        printf("Stack contains:\n");
        while (temp != NULL)
        {

            // print node data
            printf("%s\n", temp->data);

            // assign temp link to temp
            temp = temp->link;
        }
        printf("\n");
    }
}