大家好，
最近在做資料結構的練習，但有一些疑問，還請各位前輩指點，謝謝！
1. In a complete binary tree, what is the index number of the parent of
the node numbered 20?
Ans: 9 (為什麼不是10?)
2. How many comparisons would the insertion sort make on an array of
10 elements that is already in ascending order?
Ans: 7 (為什麼不是9?)