Find Inorder Successor of a node in a binary tree.

/*
    * 1. Idea is to use code of inorder traversal.
    * 2. Keep track of last processed node in lastNode pointer variable.
    * 3. While processing the current node print last process Node. Current node will be inorder successor of last node.
    * 4. Update lastNode to current processed node and repat.
    *
    * The code can be modified with little changes to return inorder successor node of a specific node.
*/

     void inorderSuccessor(node *ptr)
     {
          if(ptr)
          {
                 inorderSuccessor(ptr->getLeftChild());
                 if(lastNode)
                      cout<<"\nSuccessor of "<<lastNode->getData();
                 else
                      cout<<"\nNo predecessor of ";
                 lastNode = ptr;
                 cout<<"\t"<<ptr->getData();                                    
                 inorderSuccessor(ptr->getRightChild());
          }
     }