krahets/hello-algo · error · Error

队列为空

Error message

队列为空

What it means

Thrown by ArrayQueue.peek() ('队列为空' / queue is empty) when queSize === 0. peek() returns nums[front]; on an empty queue front is stale, so the guard prevents returning undefined-as-number. pop() calls peek() first, so pop on an empty queue surfaces the same error.

Source

Thrown at codes/typescript/chapter_stack_and_queue/array_queue.ts:58

        // 通过取余操作实现 rear 越过数组尾部后回到头部
        const rear = (this.front + this.queSize) % this.capacity;
        // 将 num 添加至队尾
        this.nums[rear] = num;
        this.queSize++;
    }

    /* 出队 */
    pop(): number {
        const num = this.peek();
        // 队首指针向后移动一位，若越过尾部，则返回到数组头部
        this.front = (this.front + 1) % this.capacity;
        this.queSize--;
        return num;
    }

    /* 访问队首元素 */
    peek(): number {
        if (this.isEmpty()) throw new Error('队列为空');
        return this.nums[this.front];
    }

    /* 返回 Array */
    toArray(): number[] {
        // 仅转换有效长度范围内的列表元素
        const arr = new Array(this.size);
        for (let i = 0, j = this.front; i < this.size; i++, j++) {
            arr[i] = this.nums[j % this.capacity];
        }
        return arr;
    }
}

/* Driver Code */
/* 初始化队列 */
const capacity = 10;
const queue = new ArrayQueue(capacity);

View on GitHub (pinned to 69932aed18)

Solutions

1. Guard with isEmpty(): if (!queue.isEmpty()) queue.pop().
2. Use while (!queue.isEmpty()) for drain loops.
3. Track enqueue/dequeue counts and never dequeue beyond the enqueued total.

Example fix

// before
const head = queue.peek(); // throws when empty
// after
if (!queue.isEmpty()) {
    const head = queue.peek();
}

function safePeek(queue) {
  return queue.isEmpty() ? undefined : queue.peek();
}

null

null

When it happens

Trigger: Calling pop() or peek() on an empty queue; a consumer loop that dequeues more items than were enqueued.

Common situations: Draining a queue without an isEmpty check; calling peek before any push; a worker that processes faster than the producer and hits an empty window.

Related errors

• 队列为空
• Queue is empty
• Queue is empty
• очередь пуста
• очередь пуста

AI-assisted analysis of krahets/hello-algo@69932aed18 (2026-08-13). Data as JSON: /api/errors/b55910c58bffb4ca. Report an issue: GitHub.