Mapping Endpoint - Design and Implement a Route Lookup API

Question

## Round 1 - Coding

## Problem

Implement an in-memory API routing engine. You register URL patterns (which may include path parameters like `/user/{id}`) and handler functions. Given an incoming request path, resolve it to the correct handler and extract path parameters.

```python
class Router:
    def add_route(
        self,
        method: str,
        pattern: str,
        handler: callable
    ) -> None:
        # pattern can include {param} placeholders
        ...

def resolve(
        self,
        method: str,
        path: str
    ) -> tuple[callable, dict[str, str]]:
        # Returns (handler, extracted_params)
        # Raises KeyError if no match
        ...
```

```
Example:
r = Router()
r.add_route("GET", "/users/{id}", get_user)
r.add_route("POST", "/users", create_user)
r.add_route("GET", "/users/{id}/posts/{pid}", get_post)

r.resolve("GET", "/users/42")           -> (get_user, {"id": "42"})
r.resolve("GET", "/users/42/posts/7")  -> (get_post, {"id": "42", "pid": "7"})
r.resolve("POST", "/users")            -> (create_user, {})
```

## Follow-ups

1. How do you handle route conflicts (e.g. `/users/new` vs `/users/{id}`)?
2. What data structure (trie vs. list) works best for large route tables?
3. How would you add wildcard routes (e.g. `/static/*filepath`)?
4. How do you handle optional path segments?

Mapping Endpoint - Design and Implement a Route Lookup API

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