12.stackUsingLL.c

/* 
    Author     : abhijithvijayan
    Title      : Stack using Linked List
*/

#include <stdio.h>
#include <stdlib.h>
int userInput();

struct Node
{
  int data;
  struct Node *link;
};

struct Node *top;

void push()
{
  int item = userInput();
  struct Node *temp = (struct Node *)malloc(sizeof(struct Node));
  temp->data = item;
  temp->link = top;
  top = temp;
}

void pop()
{
  if (top == NULL)
  {
    printf("The Stack is already empty\n");
  }
  else
  {
    struct Node *newptr = top;
    top = newptr->link;
    free(newptr);
  }
}

void view()
{
  if (top == NULL)
    printf("Empty List\n\n");
  else
  {
    struct Node *newptr = top;
    printf("\nThe list is...\n");
    while (newptr != NULL) //careful
    {
      printf("%d ", newptr->data);
      newptr = newptr->link;
    }
    printf("\n\n");
  }
}

int userInput()
{
  int item;
  printf("Enter the element:");
  scanf("%d", &item);
  return item;
}

void main()
{
  system("clear");
  int ch;
  top == NULL;
  do
  {
    printf("\n---Operations Menu---\n");
    printf("1.Push\n2.Pop\n\nEnter your choice# ");
    scanf("%d", &ch);
    switch (ch)
    {
    case 1:
      push();
      view();
      break;
    case 2:
      pop();
      view();
      break;
    }
  } while (ch < 3);
}