<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) {
        string returnVal = "";
        string* shorterString;
        string* longerString; 
        if (str1.length() > str2.length()) {
            shorterString = &str2;
            longerString = &str1;
        } else {
            shorterString = &str1;
            longerString = &str2;
        }
        std::cout << *shorterString << "\n," << *longerString << "\n";
        // try the longest possible substring then work backwards until we find one
        for (int i = shorterString->length(); i > 0; i--) {
            // start with a subsection of str1
            string testString = shorterString->substr(0, i); 
            std::cout << "Test string: " << testString << "\n";

            bool mismatchFound = false;
            //iterate through all of str2 to see if it is made up entirely of repeats
            for (int j = 0; j < longerString->length(); j+= testString.length()) {
               std::cout << "Testing from position " << j << "\n";
               if (longerString->substr(j, testString.length()) != testString) 
               {
                   mismatchFound = true;
                   cout << "mismatchFound";
                   break;
               }
            }
             for (int j = 0; j < shorterString->length(); j+= testString.length()) {
               std::cout << "Testing from position " << j << "\n";
               if (shorterString->substr(j, testString.length()) != testString) 
               {
                   mismatchFound = true;
                   cout << "mismatchFound";
                   break;
               }
            }
            if(!mismatchFound) return testString;
        }

        return returnVal;
    }
};
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