<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) 
    { 
        // base case
        if(str1 + str2 != str2 + str1)
        {
            return "";
        }
        // we know there is an answer after base case, get length and find gcd
        int len1 = str1.length();
        int len2 = str2.length();
        string ret = "";

        // find the smaller value
        // if (len1 > len2)
        // {
        //     int result = len1;
        // }
        int result = len2;

        // get the length of repetition within string
        while (result > 0) 
        { 
            if (len1 % result == 0 && len2 % result == 0) 
            { 
                break; 
            } 
            result--; 
        } 
        // with the lenght, get the repeated string
        for(int i = 0; i < result; i++)
        {
            ret = ret + str1[i];
        } 
        // return repeated string
        return ret; 
    }
};
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