Stack Explanation

Understanding Stacks in C

A stack is a linear data structure that follows the Last-In-First-Out (LIFO) principle. Think of it like a stack of plates; you can only add or remove a plate from the top. In computing terms, this means the last element added is the first element to be removed.

Key Operations

• Push: Add an item to the top.
• Pop: Remove and return the top item.
• Peek (or Top): View the top item without removing it.

Code Breakdown

The provided C code demonstrates a simple stack implementation. Here's what's happening:

1. Struct Definition:

   typedef struct {
       int items[MAX_SIZE];
       int top;
   } Stack;

   This defines a stack structure containing an array items to hold the elements and an integer top to track the index of the top element.

2. Initialization:

   void initializeStack(Stack *s) {
       s->top = -1;
   }

   This function initializes the stack's top index to -1, indicating that the stack is empty.

3. Stack Operations:

   • isFull(): Checks if the stack is full.
   • isEmpty(): Checks if the stack is empty.
   • push(): Adds an item to the top.
   • pop(): Removes and returns the top item.
   • peek(): Views the top item without removing it.

4. Main Function: In the main function, a stack s is created and initialized. We then push the numbers 5, 10, and 15 onto the stack. Subsequently, we peek to see the top of the stack (should display 15), then pop to remove the top item, and finally peek again to see the new top (should display 10).

Enhancing Learning:

Comments: The code contains inline comments to help readers understand the purpose of each function and the logic behind specific lines.

    if (isEmpty(s)) {
        printf("Stack is empty. Cannot pop.\n");
        return -1; // Assuming -1 indicates an error
    }

In the above code snippet, for example, the comment indicates that -1 is returned as an error value when trying to pop from an empty stack.