title: Find the largest number smaller than a given number(n) in the given BST
body: <p>Find the largest number smaller than a given number(n) in the given BST.</p>
  
  <p>I tried this:</p>
  
  <p>start at root node, check if root equal to n-1. If root is less than n-1  recursively call the method on root.right. If root is more than n-1 recursively call the method on root.left. </p>
  
  <p>This solution works if i have a global variable to keep track to current largest element smaller that n but this is not good solution. Please let me know how to solve without global variable</p>