🚶 队列 Queue 可视化

// 队列类实现（数组模拟）
class Queue {
    constructor() {
        this.items = [];
    }

    // 入队 - O(1)
    enqueue(item) {
        this.items.push(item);
    }

    // 出队 - O(n) 用数组实现需要搬移
    // 用链表实现为 O(1)
    dequeue() {
        if (this.isEmpty()) {
            throw new Error('Queue underflow');
        }
        return this.items.shift();
    }

    // 查看队头 - O(1)
    front() {
        return this.items[0];
    }

    isEmpty() {
        return this.items.length === 0;
    }

    size() {
        return this.items.length;
    }
}

// 循环队列实现
class CircularQueue {
    constructor(capacity) {
        this.data = new Array(capacity).fill(null);
        this.front = 0;
        this.rear = 0;
        this.capacity = capacity;
        this.count = 0;
    }

    enqueue(item) {
        if (this.isFull()) throw new Error('Queue full');
        this.data[this.rear] = item;
        this.rear = (this.rear + 1) % this.capacity;
        this.count++;
    }

    dequeue() {
        if (this.isEmpty()) throw new Error('Queue empty');
        const item = this.data[this.front];
        this.data[this.front] = null;
        this.front = (this.front + 1) % this.capacity;
        this.count--;
        return item;
    }

    isFull() { return this.count === this.capacity; }
    isEmpty() { return this.count === 0; }
}