Mask email address

Convert an email address into a partially masked string.

strings masking validation

Write a function `mask_email(email: str) -> str` that takes a well-formed email address (exactly one '@', no spaces) and returns a masked version.

To mask:
1. Split the email into `local` (before `@`) and `domain` (after `@`).
2. If the length of `local` is 1, keep that single character. If it's 2, keep the first and last character unchanged. If it's 3 or more, keep the first character, then a mask of `'*'` repeated (length of local - 2), then the last character.
3. Append the `'@'` and the domain unchanged.

For example: `mask_email("alice@example.com")` → `"a***e@example.com"`.

You may assume the input is always a valid email address: non-empty, exactly one '@', and no spaces.

Constraints

Input length: 5 to 100 characters. No uppercase letters? Actually uppercase may appear; keep them as-is. Time complexity O(len(email)), space O(len(email)).

Example

>>> mask_email("alice@example.com")
'a***e@example.com'
>>> mask_email("ab@example.com")
'ab@example.com'
>>> mask_email("a@example.com")
'a@example.com'

8 points ~10 min

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Hints

Use `email.split('@')` to separate the local part and domain.

Build the mask part with `'*' * (len(local)-2)`.

Remember to handle lengths 1 and 2 specially.

Test Results

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