8.1 Trees
-->root,children, parent, siblings, leaf; level, degree of element 的基本概念
8.2 Binary Trees
-->什么样的tree是Binary Tree
8.3. Properties of Binary Tree
-->树的节点数与height的关系
-->full binary tree 到complete binary tree的概念
-->complete binary tree中parent 和child的序号的关系:也是用formula-based方法实现binary tree的基础
8.4. Representation of Binary Trees
-->Formula-based representation: array
:only efficient when the number of missing elements is small.
-->Linked Representation
::PreOrder, InOrder, PostOrder Traversal (recursive) use stack
::LevelOrder Traversal (not recursive) use queue
::它导致一个显著逻辑,假设一个算法的各个步骤能够之一样的的stack的方式来实现,然后可以使用recursive方 式来实现,该算法。