Matching Contacts: Find Overlapping Contacts Between Two User Address Books

Question

## Problem

You are given two address books, each as a list of contact records. Each contact has a `name` and a list of `emails`. Two contacts match if they share at least one email address.

Return all matching pairs as `(name_from_book_a, name_from_book_b)`, sorted alphabetically by the first name, then second.

```python
from typing import List, Tuple

def find_matches(
    book_a: List[dict],
    book_b: List[dict]
) -> List[Tuple[str, str]]:
    # contact: {"name": str, "emails": [str, ...]}
    pass
```

**Example:**
```
book_a = [{"name": "Alice", "emails": ["alice@x.com", "a@y.com"]},
          {"name": "Bob",   "emails": ["bob@x.com"]}]
book_b = [{"name": "Alicia", "emails": ["a@y.com"]},
          {"name": "Robert", "emails": ["r@z.com"]}]

Alice and Alicia share "a@y.com" -> match
Bob and Robert share nothing -> no match

Output: [("Alice", "Alicia")]
```

## Follow-ups

1. How would you handle fuzzy name matching (e.g., "Bob" vs. "Bobby") as an additional signal?
2. What if email addresses have different capitalizations or aliasing (e.g., gmail ignores dots)?
3. How would you scale this to match two books of 10 million contacts each?
4. How would you rank matches by confidence when multiple signals (email, phone, name similarity) are available?

Matching Contacts: Find Overlapping Contacts Between Two User Address Books

Question Details

Full Details

Topics

More from Stripe