831. Masking Personal Information

Problem

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.

  Example 1:

Input: s = "LeetCode@LeetCode.com"
Output: "l*****e@leetcode.com"
Explanation: s is an email address.
The name and domain are converted to lowercase, and the middle of the name is replaced by 5 asterisks.

Example 2:

Input: s = "AB@qq.com"
Output: "a*****b@qq.com"
Explanation: s is an email address.
The name and domain are converted to lowercase, and the middle of the name is replaced by 5 asterisks.
Note that even though "ab" is 2 characters, it still must have 5 asterisks in the middle.

Example 3:

Input: s = "1(234)567-890"
Output: "***-***-7890"
Explanation: s is a phone number.
There are 10 digits, so the local number is 10 digits and the country code is 0 digits.
Thus, the resulting masked number is "***-***-7890".

  Constraints:

• s is either a valid email or a phone number. If s is an email:

• 8 <= s.length <= 40

• s consists of uppercase and lowercase English letters and exactly one '@' symbol and '.' symbol.

  If s is a phone number:

• 10 <= s.length <= 20

• s consists of digits, spaces, and the symbols '(', ')', '-', and '+'.

Solution (Java)

class Solution {
    public String maskPII(String s) {
        StringBuilder masked = new StringBuilder();
        if (Character.isAlphabetic(s.charAt(0))) {
            int locationOfAtSymbol = s.indexOf("@") - 1;
            masked.append(s.charAt(0)).append("*****").append(s.substring(locationOfAtSymbol));
            return masked.toString().toLowerCase();
        } else {
            StringBuilder allDigits = new StringBuilder();
            int pointer = -1;
            while (++pointer < s.length()) {
                if (Character.isDigit(s.charAt(pointer))) {
                    allDigits.append(s.charAt(pointer));
                }
            }
            int numDigits = allDigits.length();
            if (numDigits == 11) {
                masked.append("+*-");
            } else if (numDigits == 12) {
                masked.append("+**-");
            } else if (numDigits == 13) {
                masked.append("+***-");
            }
            masked.append("***-***-").append(allDigits.substring(numDigits - 4));
            return masked.toString();
        }
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).