<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 base=str1.size() > str2.size()?str2:str1;
        for(int l = base.size(); l>=1; l--) {
            if (isGcd(l, str1, str2)){ 
                return base.substr(0,l);
            }
        }
        return "";
    }

    bool isGcd(int l, string str1, string str2){
        if(str1.size()%l!=0 or str2.size()%l!=0) {
            return false;
        }
        return build(l, str1, str2) and build(l, str2, str1);
    }

    bool build(int l, string str, string ostr){
        string base = ostr.substr(0,l);
        cout<<"Base before"<<base<<endl;
        int fac = str.size()/l;
        cout<<"fac"<<fac<<endl;
        string res = "";
        for(int i=0; i<fac; i++){
            res+=base;
        }
        cout<<"Base after"<<res<<endl;
        cout<<"String"<<str<<endl;
        if(res==str) {
            return true;
        }
        return false;
    }
};
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