大家好，
最近在做资料结构的练习，但有一些疑问，还请各位前辈指点，谢谢！
1. In a complete binary tree, what is the index number of the parent of
the node numbered 20?
Ans: 9 (为什么不是10?)
2. How many comparisons would the insertion sort make on an array of
10 elements that is already in ascending order?
Ans: 7 (为什么不是9?)

因为 root 是 0

嗯、要看 root 是 0 还是 1 而定。

2. 应该是9 comprisons没错@@*comparisons