Find the second largest element in a Binary Search Tree

find the right most element. If this is a right node with no children, return its parent. if this
is not, return the largest element of its left child.
http://www.glassdoor.com/Interview/Find-the-second-largest-element-in-a-Binary-Search-Tree-QTN_238511.htm
Node
findSceondLargest(Node root) {
  // If tree is null or is single node only, return null (no second largest)
  if (root==null || (root.left==null && root.right==null)) return null;
  Node parent = null, child = root;
  // find the right most child
  while (child.right!=null) {
      parent = child;
      child = child.right;
   }
   // if the right most child has no left child, then it's parent is second largest
   if (child.left==null) return parent;
   // otherwise, return left child's rightmost child as second largest
   child = child.left;
   while (child.right!=null) child = child.right;
   return child;
}