C Program to Implement two Stacks using a Single Array & Check for Overflow & Underflow

Code:

#include
#define SIZE 10


int ar[SIZE];
int top1 = -1;
int top2 = SIZE;

//Functions to push data
void push_stack1 (int data)
{
  if (top1 < top2 - 1)
  {
    ar[++top1] = data;
  }
  else
  {
    printf ("Stack Full! Cannot Push\n");
  }
}
void push_stack2 (int data)
{
  if (top1 < top2 - 1)
  {
    ar[--top2] = data; 
  }
  else
  {
    printf ("Stack Full! Cannot Push\n");
  }
}

//Functions to pop data
void pop_stack1 ()
{
  if (top1 >= 0)
  {
    int popped_value = ar[top1--];
    printf ("%d is being popped from Stack 1\n", popped_value);
  }
  else
  {
    printf ("Stack Empty! Cannot Pop\n");
  }
}
void pop_stack2 ()
{
  if (top2 < SIZE)
  {
    int popped_value = ar[top2++];
    printf ("%d is being popped from Stack 2\n", popped_value);
  }
  else
  {
    printf ("Stack Empty! Cannot Pop\n");
  }
}

//Functions to Print Stack 1 and Stack 2
void print_stack1 ()
{
  int i;
  for (i = top1; i >= 0; --i)
  {
    printf ("%d ", ar[i]);
  }
  printf ("\n");
}
void print_stack2 ()
{
  int i;
  for (i = top2; i < SIZE; ++i)
  {
    printf ("%d ", ar[i]);
  }
  printf ("\n");
}

int main()
{
  int ar[SIZE];
  int i;
  int num_of_ele;

  printf ("We can push a total of 10 values\n");

  //Number of elements pushed in stack 1 is 6
  //Number of elements pushed in stack 2 is 4

  for (i = 1; i <= 6; ++i)
  {
    push_stack1 (i);
    printf ("Value Pushed in Stack 1 is %d\n", i);
  }
  for (i = 1; i <= 4; ++i)
  {
    push_stack2 (i);
    printf ("Value Pushed in Stack 2 is %d\n", i);
  }

  //Print Both Stacks
  print_stack1 ();
  print_stack2 ();

  //Pushing on Stack Full
  printf ("Pushing Value in Stack 1 is %d\n", 11);
  push_stack1 (11);

  //Popping All Elements From Stack 1
  num_of_ele = top1 + 1;
  while (num_of_ele)
  {
    pop_stack1 ();
    --num_of_ele;
  }

  //Trying to Pop From Empty Stack
  pop_stack1 ();

  return 0;
}


Output:

We can push a total of 10 values
Value Pushed in Stack 1 is 1
Value Pushed in Stack 1 is 2
Value Pushed in Stack 1 is 3
Value Pushed in Stack 1 is 4
Value Pushed in Stack 1 is 5
Value Pushed in Stack 1 is 6
Value Pushed in Stack 2 is 1
Value Pushed in Stack 2 is 2
Value Pushed in Stack 2 is 3
Value Pushed in Stack 2 is 4
6 5 4 3 2 1 
4 3 2 1 
Pushing Value in Stack 1 is 11
Stack Full! Cannot Push
6 is being popped from Stack 1
5 is being popped from Stack 1
4 is being popped from Stack 1
3 is being popped from Stack 1
2 is being popped from Stack 1
1 is being popped from Stack 1
Stack Empty! Cannot Pop

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