title: Time complexity of loops iterating over related sets
body: <p>Here I come again with basic questions :(</p>
  
  <p>If I have the next pseudo-code:</p>
  
  <pre><code>iterate over set (A)
      //some *O(1)* operations
  
  iterate over set (B)
      //another *O(1)* operations
  </code></pre>
  
  <p>From what I have learned, the time would be <em>O(numberOfElementsInA + numberOfElementsInB)</em></p>
  
  <p>However, If I know that <em>B</em> is subset of <em>A</em> and <em>numberOfElementsInA</em> is always greater or equal than 
  <em>numberOfElementsInB</em>, can I simplify the time by writing just <em>O(numberOfElementsInA)</em> ?</p>