<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) {
        
        string s1 = "";
        string s2 = "";
        for (auto ch : s) {
            if ('0' <= ch and ch <= '9') {
                s1 += ch;
            }
            else{
                s2 += ch;
            }
        }

        int n = s1.size();
        int m = s2.size();
        if (abs(n-m) > 1) {
            return "";
        }
        
        s = "";
        if ( n >= m ) {
            for ( int i = 0; i < n; i++ ) {
                if (i < s1.size()) {
                    s += s1[i];
                }
                if (i < s2.size()) {
                    s += s2[i];
                }
            }
        }
        else {
            for ( int i = 0; i < m; i++ ) {
                if (i < s2.size()) {
                    s += s2[i];
                }
                if (i < s1.size()) {
                    s += s1[i];
                }
            }
        }
        return s;
    }
};
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