How many internal nodes does this tree have?
ANS
Anything that is not a leaf node is an internal node. Internal nodes might have 1 or 2 children.
How many leaf nodes does this tree have?
ANS
Anything that has no children is a leaf node.
How many nodes in the tree have at least one sibling?
ANS
Siblings must have the same parent. If a node has two children, then each such child has a sibling.
How many descendents does the root of this tree have?
ANS
Every node except the root is a descendent.
What is the height of this tree?
Count the number of steps to the deepest node, and add 1.
What is the depth of this tree?
Nodes have depth.
Which statement is correct?
Do any internal nodes have only one child? If so, the tree is not full.
A complete tree fills in nodes level by level, with the bottom level filled in from left to right.