<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 temp;
        string output;
        int w1 = str1.size();
        int w2 = str2.size();

        string *larger;
        string *smaller;
        int times = 0;
        int small;
        if (w1>w2) {
            larger = &str1;
            smaller = &str2;
            times = w1/w2;
            small=w2;
        } else {
            larger=&str2;
            smaller=&str1;
            times = w2/w1;
            small=w1;
        }

        // first check if the whole string can be used 
        while(times > 0) {
            temp += (*smaller);
            times--;
        }

        if (temp == *larger) {
            return *smaller;
        }

        int len = small/2;
        temp = smaller->substr(0, small/2);
        while(len > 0) {

            if (CommonDenominator(temp, str1) && CommonDenominator(temp, str2)) {
                return temp;
            }
            temp.pop_back();
            len--;
        }



        return "";
    }

    bool CommonDenominator(string test, string main) {
        int w1 = test.size();
        int w2 = main.size();
        string temp; 
        int times = w2/w1;
        while(times > 0) {
            temp += test;
            times--;
        }

        if (temp == main) {
            return true;
        }

        return false;
    }
};
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