数据库树算法（数据结构-树）

发现国内好多教材对树的解释含含糊糊，找了下英文原版，理解就没那么费劲了

结点的level：The level of a node is defined by ０ (the number of connections between the node and the root).

结点的高度（Height）：The height of a node is the number of edges on the longest path between that node and a leaf.

树的高度：The height of a tree is the height of its root node.

结点的深度（Depth of node）：The depth of a node is the number of edges from the tree's root node to the node.

结点的度（Degree）：The number of sub trees of a node.

叶子（Leaf）：A node with no children.

二叉树的性质：

（1）若二叉树的层次从0开始，则在二叉树的第i层至多有2^i个结点(i>=0)。

（2）高度为k的二叉树最多有2^(k 1) - 1个结点(k>=-1)。 (空树的高度为-1)

（3）对任何一棵二叉树，如果其叶子结点(度为0)数为m, 度为2的结点数为n, 则m = n 1。

完美二叉树(Perfect Binary Tree)

完全二叉树(Complete Binary Tree)

A Complete Binary Tree （CBT) is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.

完满二叉树(Full Binary Tree)