831. Masking Personal Information

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.

class Solution {
    string email(string s) {
        string res = "";
        for(int i = 0; i < s.length(); i++) {
            if(isalpha(s[i])) s[i] = tolower(s[i]);
        }
        auto pos = s.find('@');
        res = string(1,s[0]) + "*****" + s.substr(pos-1);
        return res;
    }
    string phone(string s) {
        int count = 0;
        for(int i = 0; i < s.length(); i++) {
            if(isdigit(s[i])) count++;
        }
        string res = "";
        for(int i = s.length() - 1; i >= 0 and res.length() < 4; i--) {
            if(isdigit(s[i]))
               res.push_back(s[i]);
        }
        reverse(begin(res),end(res));
        if(count == 10) return "***-***-" + res;
        if(count == 11) return "+*-***-***-" + res;
        if(count == 12) return "+**-***-***-" + res;
        return "+***-***-***-" + res;
    }
public:
    string maskPII(string s) {
        return s.find('@') != string::npos ? email(s) : phone(s);
    }
};