title: What is the time complexity of __gcd?
body: <p>What is the time complexity of __gcd(m,n) function? Also, does it use the Euclidean method to calculate gcd?</p>
  
  <p>e.g. code</p>
  
  <pre><code>#include &lt;iostream&gt; 
  #include &lt;algorithm&gt; 
  
  using namespace std; 
  
  int main() { 
      cout &lt;&lt; "gcd(10, 25) : " &lt;&lt; __gcd(6, 20) &lt;&lt; endl; 
  } 
  </code></pre>