Why does function preorder2() presented in the Traversal module make only half as many recursive calls as function preorder()?

Because half of the pointers are null
  • Because there are half as many nodes
  • Because there are half as many leaf nodes
  • Because only internal nodes get called

All nodes will eventually get called

The number of nodes in the tree does not change based on the algorithm used to traverse it.

The Full Binary Tree Theorem tells us that roughly half of all pointers in a binary tree are null. No recursive call is made for these pointers by preorder2.