NOTE:
- For bstNumLeaves, bstRange and bstLevelOrder, your time complexities
  should be in terms of either:
  - n, where n is the number of nodes in the tree, or
  - h, where h is the height of the tree

- For numCommonValues, your time complexity should be in terms of one or
  more of the following:
  - n1 (the number of nodes in t1)
  - h1 (the height of t1)
  - n2 (the number of nodes in t2)
  - h2 (the height of t2)

=================
  bstNumLeaves
=================

- Worst-case time complexity: O(...)

- Explanation: ...

=================
    bstRange
=================

- Worst-case time complexity: O(...)

- Explanation: ...

=================
  bstLevelOrder
=================

- Worst-case time complexity: O(...)

- Explanation: ...

=================
 numCommonValues
=================

- Worst-case time complexity: O(...)

- Explanation: ...