<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:
    bool divisor(string divisor , string str){
        while(str.length()>=divisor.length()){
            if(str.find(divisor)!= string::npos){
                int x = str.find(divisor);
                if(x!=0){
                    return false;
                }
                str.erase(x,divisor.length());
            }
            else{
                return false;
            }
        }
        if(str.length()>0){
            return false;
        }
        return true;
    }
    string gcdOfStrings(string str1, string str2) {
        string ans="";
        if(str1.length()>=str2.length()){
            int len = str2.length();
            while(len>0){
                string x = str2.substr(0,len);
                if(divisor(x,str2)){
                    if(divisor(x,str1)){
                        ans=x;
                        break;
                    }
                }
                len--;
            }
        }
        else{
            int len = str1.length();
            while(len>0){
                string x = str1.substr(0,len);
                if(divisor(x,str1)){
                    if(divisor(x,str2)){
                        ans=x;
                        break;
                    }
                }
                len--;
            }
        }
        return ans;
    }
};
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