Stack Visualizer

What is the isEmpty Operation in Stack?

The isEmpty operation checks whether a stack contains any elements or not. It's a fundamental operation that helps prevent errors when trying to perform operations like pop() or peek() on an empty stack.

How Does It Work?

Consider a stack represented as an array:[] (empty) or[5, 3, 8] (with elements).

For an empty stack [],isEmpty() returnstrue
For a non-empty stack [5, 3, 8],isEmpty() returnsfalse

The operation simply checks if the stack's size/length is zero.

Algorithm Implementation

Check the current size/length of the stack
Return the result:
- true if size equals 0
- false otherwise

Time Complexity

O(1) constant time complexity
The operation only needs to check one value (size/length) regardless of stack size

Practical Usage

Prevent stack underflow errors before pop() operations
Check if there are elements to process
Validate stack state in algorithms
Terminate processing loops when stack becomes empty

Example: Before popping an element, always check:
if (!stack.isEmpty()) element = stack.pop();

The isEmpty operation is a simple but crucial part of stack implementation, ensuring safe stack manipulation and preventing runtime errors.

Visualize Push, Pop, Peek, and IsEmpty operations

Stack Visualization

Stack is empty

Stack isEmpty Operation Implementation

// Stack Implementation with isEmpty Operation in JavaScript
class Stack {
  constructor() {
    this.items = [];
    this.top = -1;
  }

  // Push operation
  push(element) {
    this.items[++this.top] = element;
    console.log(`Pushed: ${element}`);
  }

  // Pop operation
  pop() {
    if (this.isEmpty()) {
      console.log("Stack Underflow - Cannot pop from empty stack");
      return -1;
    }
    return this.items[this.top--];
  }

  // Check if stack is empty
  isEmpty() {
    const empty = this.top === -1;
    console.log(`Stack is ${empty ? "empty" : "not empty"}`);
    return empty;
  }

  // Display stack
  display() {
    console.log("Current Stack:", this.items.slice(0, this.top + 1));
  }
}

// Usage
const stack = new Stack();
console.log("Initial stack check:");
stack.isEmpty();  // true

stack.push(10);
stack.push(20);
stack.display();
stack.isEmpty();  // false

stack.pop();
stack.pop();
stack.isEmpty();  // true