<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) {
        int longer = str1.length() > str2.length() ? str1.length() : str2.length();
        bool failed = false;
        int len = longer;
        string divisor = str1.substr(0, len);

        for(int i = 0; i < longer+1; i+=len){
            
            if(failed){
                i=0;
                len--;
                if(len == 0){
                    return "";
                }
                divisor = str1.substr(i, len);
                failed = false;
            }
            if(longer % len == 0){
                std::cout << " len: " << len << " i: " << i << "\n";
                
                if(str1.length() > i){
                    // std::cout << "str1 is less than i, checking if " << str1.substr(i, len) << " = " << divisor << "\n";
                    if(str1.substr(i, len) != divisor){
                        // std::cout << "false, next factor \n";
                        failed = true;
                    }
                }
        
                if(str2.length() > i){
                    // std::cout << "str2 is less than i, checking if " << str2.substr(i, len) << " = " << divisor << "\n";
                    if(str2.substr(i, len) != divisor){
                        // std::cout << "false, next factor \n";
                        failed = true;
                    }
                }

            }
            // if not a factor, its not going to fit
            else{
                failed = true;
            }
        }
        
        return divisor;
    }
};
25060