Today , let’s understand Stacks and Queues in detail:
📦 What is a Stack?
Think of a stack like a stack of plates:
- You add a new plate on top
- You remove the plate from the top
This is called LIFO → Last In, First Out
Key Operations:
✅ push() → Add an item to the top
✅ pop() → Remove the top item
✅ peek() → See the top item without removing
✅ isEmpty() → Check if the stack is empty
Real-Life Examples:
- Undo in a text editor
- Browser back button
- Recursion calls
Example in Code (JavaScript):
js
let stack = [];
stack.push(1); // Add 1
stack.push(2); // Add 2
stack.pop(); // Removes 2
console.log(stack); // [1]
🌀 What is a Queue?
A queue works like a line at the supermarket:
- The first person in line is served first
This is called FIFO → First In, First Out
Key Operations:
✅ enqueue() → Add to the end
✅ dequeue() → Remove from the front
✅ peek() → See who’s first
✅ isEmpty() → Check if queue is empty
Real-Life Examples:
- Waiting list
- Print queue
- Customer service calls
Example in Code (JavaScript):
js
let queue = [];
queue.push(“A”); // Enqueue A
queue.push(“B”); // Enqueue B
queue.shift(); // Dequeue A
console.log(queue); // [“B”]
🔄 Advanced Types
- Circular Queue → Saves space by reusing empty spots
- Deque → Add/remove from both ends
- Priority Queue → Items come out based on importance, not just order
✅ When to Use
- Stack: When you need to reverse something or go back
- Queue: When you need to process in order, like first come, first served
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