TikTok / VO 面试真题解析：Caching Reader 与 Balanced Brackets

Implement a caching reader for remote file access. A RemoteReader can read bytes from a server by offset and size. Your task is to implement CachingReader so that repeated reads minimize calls to the remote reader by caching data locally.

Then solve a second question: given a string containing only brackets such as { and }, implement a function isBalanced that returns a boolean indicating whether the string is balanced.

Question 1: Caching Reader

class RemoteReader:
    def read(self, offset: int, size: int) -> bytes:
        # already implemented, you can call this method

class CachingReader:
    # Maximum memory used by a caching reader
    # MaxCacheSize: int = 10000

    def read(self, offset: int, size: int) -> bytes:
        # TODO: implement this method

    def __init__(self):
        # TODO: feel free to add anything you like
        self.__reader = RemoteReader()

Question 2: Balanced Brackets

Input: String containing { and }

• Balanced → true
• Non-balanced → false

Write a function isBalanced(str: String) -> Boolean.

这道题包含两个经典面试方向：第一个是实现带缓存的远程读取器，需要在本地保存已经读过的数据，尽量减少对远端 <code>RemoteReader</code> 的重复访问，核心思路通常是用区间缓存或按块缓存来覆盖请求范围；第二个是括号匹配，输入只包含 <code>{</code> 和 <code>}</code> 时，可以用计数器或栈来判断是否始终保持前缀合法，最终计数归零即为平衡。第一个问题更强调缓存命中、区间合并和内存上限控制，第二个问题则考察基础的栈 / 计数判断能力。