Find an Exit in a URL Maze
Company: Ramp
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Technical Screen
You are given a starting URL for a web-based maze. Each URL represents one room in the maze. Your task is to write a program that discovers whether there is a path from the starting room to an exit room.
Assume you have a helper function or HTTP client that can request a room URL. A successful response has status code `200` and returns JSON in this shape:
```json
{
"is_exit": false,
"neighbors": ["https://maze.example/room/2", "https://maze.example/room/7"]
}
```
A room is an exit if `is_exit` is `true`. The maze may contain cycles, so your solution must not revisit the same URL indefinitely.
Implement:
```python
def find_exit(start_url: str) -> str | None:
pass
```
Return the URL of any exit room reachable from `start_url`, or `None` if no exit is reachable.
Follow-up: The maze service is unreliable and protected by per-room access keys.
Additional behavior:
1. A request may return `503 Service Unavailable`. In that case, retry the same URL a limited number of times before treating it as temporarily unreachable.
2. A request may return `401 Unauthorized`. Some successful room responses may include a key, for example:
```json
{
"is_exit": false,
"neighbors": ["https://maze.example/room/9"],
"key": "abc123"
}
```
When a key is returned, capture it and include it in future requests using a header such as:
```text
Authorization: Bearer abc123
```
Update your implementation so it can still find an exit while handling cycles, retries, `503` responses, `401` responses, and authorization keys.
Quick Answer: This question evaluates graph traversal and state-management skills, emphasizing handling cycles, HTTP error conditions, retry logic, and propagation of authorization tokens in a networked client.