DSA using JavaScript

Time Complexity: Push : O(1) (constant time to enqueue). Pop : O(n) (transfer elements from queue1 to queue2 ). Top : O(n) (same logic as pop ). Empty : O(1) (constant time to check if a queue is empty).
Space Complexity: O(n), where n is the total number of elements.

Queue

class MyStack {
  constructor() {
    this.queue1 = [];
    this.queue2 = [];
  }

  push(x) {
    this.queue1.push(x); // Add element to queue1
  }

  pop() {
    while (this.queue1.length > 1) {
      this.queue2.push(this.queue1.shift()); // Transfer all but the last element to queue2
    }
    const poppedElement = this.queue1.shift(); // Last element of queue1 is the top of the stack
    this.swapQueues();
    return poppedElement;
  }

  top() {
    while (this.queue1.length > 1) {
      this.queue2.push(this.queue1.shift()); // Transfer all but the last element to queue2
    }
    const topElement = this.queue1.shift(); // Last element of queue1 is the top of the stack
    this.queue2.push(topElement); // Push it back to queue2
    this.swapQueues();
    return topElement;
  }

  empty() {
    return this.queue1.length === 0;
  }

  swapQueues() {
    [this.queue1, this.queue2] = [this.queue2, this.queue1]; // Swap queue1 and queue2
  }
}

// Example Usage
const myStack = new MyStack();
myStack.push(1);
myStack.push(2);
console.log(myStack.top());  // Output: 2
console.log(myStack.pop());  // Output: 2
console.log(myStack.empty()); // Output: false