<p>You are given an alphanumeric string <code>s</code>. (<strong>Alphanumeric string</strong> is a string consisting of lowercase English letters and digits).</p>

<p>You have to find a permutation of the string where no letter is followed by another letter and no digit is followed by another digit. That is, no two adjacent characters have the same type.</p>

<p>Return <em>the reformatted string</em> or return <strong>an empty string</strong> if it is impossible to reformat the string.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;a0b1c2&quot;
<strong>Output:</strong> &quot;0a1b2c&quot;
<strong>Explanation:</strong> No two adjacent characters have the same type in &quot;0a1b2c&quot;. &quot;a0b1c2&quot;, &quot;0a1b2c&quot;, &quot;0c2a1b&quot; are also valid permutations.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;leetcode&quot;
<strong>Output:</strong> &quot;&quot;
<strong>Explanation:</strong> &quot;leetcode&quot; has only characters so we cannot separate them by digits.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;1229857369&quot;
<strong>Output:</strong> &quot;&quot;
<strong>Explanation:</strong> &quot;1229857369&quot; has only digits so we cannot separate them by characters.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 500</code></li>
	<li><code>s</code> consists of only lowercase English letters and/or digits.</li>
</ul>

class Solution {
public:
    string reformat(string s) {
        
        int digitsVsLetters {};

        for(int i = 0; i < s.size(); ++i) if(isalpha(s[i])) ++digitsVsLetters; else --digitsVsLetters;
        if(digitsVsLetters < -1 || digitsVsLetters > 1) return "";

        int pointerLetter {};
        int pointerDigit {};
        std::string reformatedString {};

        for(int i = 0; i < s.size() / 2; ++i){
            if(digitsVsLetters == 1){
                while(!isalpha(s[pointerLetter])) ++pointerLetter;
                reformatedString.push_back(s[pointerLetter++]);
                while(isalpha(s[pointerDigit])) ++pointerDigit;
                reformatedString.push_back(s[pointerDigit++]);
            } else {
                while(isalpha(s[pointerDigit])) ++pointerDigit;
                reformatedString.push_back(s[pointerDigit++]);
                while(!isalpha(s[pointerLetter])) ++pointerLetter;
                reformatedString.push_back(s[pointerLetter++]);
            }
            
        }

        if(digitsVsLetters == 1) {while(!isalpha(s[pointerLetter])) ++pointerLetter; reformatedString.push_back(s[pointerLetter++]);}
        else if(digitsVsLetters == -1) {while(isalpha(s[pointerDigit])) ++pointerDigit;; reformatedString.push_back(s[pointerDigit++]);}

        return reformatedString;
    }
};
9000