title: Find the second maximum number in an array with the smallest complexity
body: <p>Tried to googled it but with no luck.
  How can I find the second maximum number in an array with the <strong>smallest complexity</strong>?</p>
  
  <p>code OR idea will be much help.</p>
  
  <p>I can loop through an array and look for the maximum number 
  after that, I have the maximum number and then loop the array again to find the second the same way.</p>
  
  <p>But for sure it is not efficient.</p>