title: Why lookup in a Binary Search Tree is O(log(n))?
body: <p>I can see how, when looking up a value in a <strong>BST</strong> we leave half the tree everytime we compare a node with the value we are looking for.</p>
  
  <p>However I fail to see why the time complexity is <code>O(log(n))</code>. So, my question is:</p>
  
  <p>If we have a tree of N elements, why the time complexity of looking up the tree and check if a particular value exists is O(log(n)), how do we get that?</p>