Masking Personal Information

Masking Personal Information - Problem

String Medium

You are given a personal information string s, representing either an email address or a phone number. Return the masked personal information using the below rules.

Email address:
An email address is:
• A name consisting of uppercase and lowercase English letters, followed by
• The '@' symbol, followed by
• The domain consisting of uppercase and lowercase English letters with a dot '.' somewhere in the middle (not the first or last character).

To mask an email:
• The uppercase letters in the name and domain must be converted to lowercase letters.
• The middle letters of the name (i.e., all but the first and last letters) must be replaced by 5 asterisks "*****".

Phone number:
A phone number is formatted as follows:
• The phone number contains 10-13 digits.
• The last 10 digits make up the local number.
• The remaining 0-3 digits, in the beginning, make up the country code.
• Separation characters from the set {'+', '-', '(', ')', ' '} separate the above digits in some way.

To mask a phone number:
• Remove all separation characters.
• The masked phone number should have the form:
"***-***-XXXX" if the country code has 0 digits.
"+*-***-***-XXXX" if the country code has 1 digit.
"+**-***-***-XXXX" if the country code has 2 digits.
"+***-***-***-XXXX" if the country code has 3 digits.
"XXXX" is the last 4 digits of the local number.

Input & Output

Example 1 — Email Masking

$ Input: s = "LeetCode@LeetCode.com"

› Output: "l*****e@leetcode.com"

💡 Note: Email detected by '@' symbol. Convert to lowercase, mask middle of name 'LeetCode' → 'l*****e', keep domain 'leetcode.com'

Example 2 — Phone with Country Code

$ Input: s = "1(234)567-890"

› Output: "***-***-7890"

💡 Note: Phone number with 10 digits total. Country code = 0 digits (no country code), local number is all 10 digits. Format: ***-***-XXXX where XXXX = 7890

Example 3 — Simple Phone

$ Input: s = "123-45-6789"

› Output: "***-***-6789"

💡 Note: Phone number with exactly 10 digits. No country code (0 digits). Format: ***-***-XXXX where XXXX = 6789

Constraints

s is either a valid email or a valid phone number
If s is an email: 3 ≤ s.length ≤ 40
If s is a phone number: 10 ≤ s.length ≤ 20

Visualization

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Asked in

G Google 15 a Amazon 12 f Facebook 8

The key insight is to use the '@' symbol to distinguish between email and phone number, then apply type-specific masking rules. For emails, convert to lowercase and mask the middle characters of the name with 5 asterisks. For phone numbers, extract digits and format based on country code length. Best approach uses string operations for O(n) time and O(n) space.

Common Approaches

✓ Binary Search

⏱️ Time: N/A Space: N/A

Sort First

⏱️ Time: N/A Space: N/A

Character-by-Character Processing

⏱️ Time: O(n) Space: O(n)

Iterate through each character to determine if the input is an email (contains '@') or phone number, then manually build the masked version character by character.

String Operations Approach

⏱️ Time: O(n) Space: O(n)

Leverage string indexOf/contains methods to quickly identify email vs phone, then use substring operations and string building for efficient masking.

Algorithm Steps — Algorithm Steps

Code -

solution.c — C

Time & Space Complexity

Time Complexity

⏱️

✓ Linear Growth

Space Complexity

⚡ Linearithmic Space

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Medium Frequency

~15 min Avg. Time

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Smart Actions

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