<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:
   // Helper function to repeat a string `n` times
string repeatString(const string& str, int n) {
    string result;
    for (int i = 0; i < n; ++i) {
        result += str;
    }
    return result;
}

// Function to check if a given substring `ss` divides both str1 and str2
bool anss(const string& ss, const string& str1, const string& str2) {
    int n = ss.size();
    if (str2.size() % n == 0 && str1.size() % n == 0) {
        string f1 = repeatString(ss, str2.size() / n);
        string f2 = repeatString(ss, str1.size() / n);
        if (f1 == str2 && f2 == str1) {
            return true;
        }
    }
    return false;
}

string gcdOfStrings(string str1, string str2) {
    if (str2.size() > str1.size()) {
        swap(str1, str2);
    }

    for (int i = str2.size(); i >= 1; i--) {
        if (anss(str2.substr(0, i), str1, str2)) {
            return str2.substr(0, i);
        }
    }
    return "";
}
};
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