<p>For two strings <code>s</code> and <code>t</code>, we say &quot;<code>t</code> divides <code>s</code>&quot; if and only if <code>s = t + t + t + ... + t + t</code> (i.e., <code>t</code> is concatenated with itself one or more times).</p>

<p>Given two strings <code>str1</code> and <code>str2</code>, return <em>the largest string </em><code>x</code><em> such that </em><code>x</code><em> divides both </em><code>str1</code><em> and </em><code>str2</code>.</p>

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

<pre>
<strong>Input:</strong> str1 = &quot;ABCABC&quot;, str2 = &quot;ABC&quot;
<strong>Output:</strong> &quot;ABC&quot;
</pre>

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

<pre>
<strong>Input:</strong> str1 = &quot;ABABAB&quot;, str2 = &quot;ABAB&quot;
<strong>Output:</strong> &quot;AB&quot;
</pre>

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

<pre>
<strong>Input:</strong> str1 = &quot;LEET&quot;, str2 = &quot;CODE&quot;
<strong>Output:</strong> &quot;&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= str1.length, str2.length &lt;= 1000</code></li>
	<li><code>str1</code> and <code>str2</code> consist of English uppercase letters.</li>
</ul>

class Solution {
public:
    string gcdOfStrings(string str1, string str2) {
        for(int i = 0; i < str2.length(); i++){
            string currentStr = str2.substr(0, str2.length()-i);
            if(str1.length() % currentStr.length() != 0 || str2.length() % currentStr.length() != 0) continue;
            bool isSub = true;
            for(int j = 0; j < str2.length(); j += currentStr.length()){
                string ccStr = str2.substr(j, currentStr.length());
                if(ccStr != currentStr){
                    isSub = false;
                    break;
                }
            }
            for(int j = 0; j < str1.length() && isSub == true; j += currentStr.length()){
                string ccStr = str1.substr(j, currentStr.length());
                if(currentStr != ccStr) {
                    isSub = false;
                    break;
                }
            }
            if(isSub) return currentStr;
        }

        return "";
    }
};
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