Stack

The Stack is a linear data structure that follows the Last-In-First-Out (LIFO) principle. In a stack, elements are inserted and removed from the same end, which is called the top.

Basic Operations

The basic operations that can be performed on a stack are:

• init: Initializes the stack.
• push: Inserts an element at the top of the stack.
• pop: Removes and returns the element at the top of the stack.
• peek: Returns the element at the top of the stack without removing it.
• isEmpty: Checks if the stack is empty.
• isFull: Checks if the stack is full.
• cleanup: Clears the stack.

Usage

To use the stack implementation, you need to include the stack.h header file in your program:

#include "stack.h"

You can push elements into the stack using the push function:

push(&stack, 10);
push(&stack, 20);
push(&stack, 30);

You can check if the stack is empty using the isEmpty function:

if (isEmpty(&stack)) {
  // The stack is empty.
} else {
  // The stack is not empty.
}

You can get the element at the top of the stack without removing it using the peek function:

int top = peek(&stack);
if (top != -1) printf("The top of the stack is %d.\n", top);

You can remove the element at the top of the stack using the pop function:

int value = pop(&stack);
if (value != -1) printf("The removed element is %d.\n", value);

Finally, you can clear the stack using the cleanup function:

cleanup(&stack);

Example

Here is an example usage of the stack implementation in C:

#include <stdio.h>
#include "stack.h"

int main() {
  Stack stack;
  init(&stack);

  // Test pushing and peeking items
  push(&stack, 10);
  push(&stack, 20);
  push(&stack, 30);
  printf("Peek: %d\n", peek(&stack)); // Should print 30

  // Test popping items
  int item = pop(&stack);
  printf("Popped item: %d\n", item); // Should print 30
  printf("Peek after pop: %d\n", peek(&stack)); // Should print 20

  // Test checking if stack is empty
  printf("Is empty: %d\n", isEmpty(&stack)); // Should print 0 (false)
  pop(&stack);
  pop(&stack);
  printf("Is empty: %d\n", isEmpty(&stack)); // Should print 1 (true)

  // Test cleaning up the stack
  cleanup(&stack);

  return 0;
}

Note

The maximum size of the stack is defined by the constant MAX_SIZE in the stack.h header file.