开放爱电面

两轮，一轮design一轮coding

Design:

PC Game Store and Launcher
Design the backend architecture for a Steam-like PC game store and desktop launcher.
You can think of the system as a combination of:

• An e-commerce store for browsing and purchasing games.
• A digital entitlement system that tracks which games each user owns.
• A large-file
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  ign和high level design全部cover，再开始deep dive。
  
  Coding:
  
  Elevator scheduling
  
  Part 1.
  
  
  
  Part 2.
  
  还有Part 3，但我在Part 2就没debug完，就没看到part 3了。有代码模板：
  
  models.py:
  
  2. from dataclasses import dataclass, field
  4. # NB: A floor/level is 0-indexed for coding simplicity even though IRL we usually
  5. # refer to the first floor as floor 1. Keep that in mind for debugging / printing.
  7. @dataclass
  8. class Person:
  9.     id: str
  10.     """Just an identifier of an individual person."""
  12.     src: int
  13.     """The floor the person started on when they called the elevator."""
  15.     dst: int
  16.     """The floor the person is trying to get to."""
  18.     def __str__(self) -> str:
  19.         return f"{self.id}({self.src}->{self.dst})"
  21. @dataclass
  22. class Floor:
  23.     level: int
  24.     """Which level does this floor represent?"""
  26.     people: list[Person] = field(default_factory=list)
  27.     """The people on this floor currently waiting for an elevator."""
  29. @dataclass
  30. class Elevator:
  31.     """You can add/remove/modify fields as you'd like here."""
  33.     id: str
  34.     """Just an identifier of an individual elevator."""
  36.     curr_floor: Floor
  37.     """The elevator's current floor."""
  39.     passengers: list[Person] = field(default_factory=list)
  40.     """The people in this elevator right now."""
  42.     direction: int = 1
  43.     """
  44.     The elevator's direction.
  45.     1 is up, -1 is down, but you can change this as you'd like or use some other
  46.     convention.
  47.     """
  49.     def __str__(self) -> str:
  50.         passengers_str = ",".join([str(person) for person in self.passengers])
  51.         match self.direction:
  52.             case 0:
  53.                 dir_str = "↔"
  54.             case 1:
  55.                 dir_str = "↑"
  56.             case -1:
  57.                 dir_str = "↓"
  58.             case _:
  59.                 raise Exception(f"Unknown direction {self.direction}")
  60.         return f"{dir_str}[{passengers_str}]"
  62. @dataclass
  63. class Building:
  64.     elevators: list[Elevator]
  66.     @property
  67.     def elevator(self) -> Elevator:
  68.         """
  69.         For parts 1-3, there is only 1 elevator, so use this accessor for convenience.
  70.         """
  72.         return self.elevators[0]
  74.     floors: list[Floor]
  76.     @property
  77.     def num_floors(self) -> int:
  78.         return len(self.floors)
  80. @dataclass
  81. class _World:
  82.     building: Building
  83.     tick_to_calls: dict[int, list[Person]]
  84.     tick: int = 0

  复制代码
  loop.py
  2. from typing import Callable
  4. from animation import animate
  5. from models import Building, _World
  7. def _is_simulation_over(world: _World) -> bool:
  8.     if world.tick <= max(world.tick_to_calls.keys()):
  9.         return False
  11.     for elevator in world.building.elevators:
  12.         if len(elevator.passengers) > 0:
  13.             return False
  15.     for floor in world.building.floors:
  16.         if len(floor.people) > 0:
  17.             return False
  19.     return True
  21. def run_simulation(
  22.     world: _World,
  23.     do_tick_fn: Callable[[Building], None],
  24.     debug: bool = False,
  25. ) -> _World:
  26.     """
  27.     Runs the elevator simulation until complete.
  28.     """
  30.     while True:
  31.         for person_calling in world.tick_to_calls[world.tick]:
  32.             world.building.floors[person_calling.src].people.append(person_calling)
  34.         if debug:
  35.             animate(world)
  37.         do_tick_fn(world.building)
  38.         world.tick += 1
  40.         print("current level:", world.building.elevators[0].curr_floor.level)
  41.         if _is_simulation_over(world):
  42.             break
  44.     if debug:
  45.         animate(world)
  47.     return world

  复制代码
  part1.py, part2.py
  2. from models import Building
  4. def do_tick(building: Building) -> None:
  5.   pass

  复制代码

感谢分享，请问是这周面的吗？

Thanks for sharing — for the design round, did it stay mostly high-level or go into a deep dive, and for the elevator coding, could you run the code on a shared screen while you debugged Part 2?

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电梯调度这题 part2 没 debug 完确实亏。想问下 design 那轮的 entitlement 系统，面试官有追问并发购买同一游戏的幂等问题吗？顺便 mark 蹲一个后续。

I0l 发表于 2026-10-30 19:55:51
电梯调度这题 part2 没 debug 完确实亏。想问下 design 那轮的 entitlement 系统，面试官有追问并发购买同一游戏的幂等问题吗？顺便

有问到失败重试的幂等

匿名用户 发表于 2026-10-30 17:41:44
感谢分享，请问是这周面的吗？

是的

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游客，您好！
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游客，您好！
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哇感谢分享

这俩题都没见过 感谢dp！