title: Find a missing number in an integer array
body: <p>I am given a supposedly consecutive array such as this:</p>
  
  <pre><code>{4,5,7,8,9,10} // missing 6
  </code></pre>
  
  <p>And I am supposed to efficiently find the missing 6.</p>
  
  <p>I have thought of doing a binary search, and checking the mid +1, mid -1.</p>
  
  <p>But I keep thinking there would be so many base cases. I keep failing...</p>
  
  <p>This shouldn't be such a hard problem but I do not know why I am struggling so hard :/</p>
  
  <p>Could someone guide me through this one??</p>
  
  <p>Thanks so much guyz</p>