Double-ended Queue

Add/remove from both ends. Useful for sliding window problems or when you need both stack and queue behavior.

class Deque {
  private items: number[];

  constructor() {
    this.items = [];
  }

  // Add to front
  addFront(item: number): void {
    this.items.unshift(item);
  }

  // Add to back
  addBack(item: number): void {
    this.items.push(item);
  }

  // Remove from front
  removeFront(): number | undefined {
    return this.items.shift();
  }

  // Remove from back
  removeBack(): number | undefined {
    return this.items.pop();
  }
}

const deque = new Deque();
deque.addBack(1); // [1]
deque.addFront(2); // [2, 1]
deque.addBack(3); // [2, 1, 3]
console.log(deque.removeFront()); // Output: 2  (now [1, 3])
console.log(deque.removeBack()); // Output: 3  (now [1])

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