树
树有节点，父子关系，叶，根，深度，高度，度
1
/ \
2 3
/ \ \
4 5 6上述实例中：
1 是根， 高度为2，深度为0 ，度为2
2，3 是节点，高度为1，深度为1 ，度分别为2，1
4，5，6 是叶， 高度为0，深度为2
1是2，3的父节点
同理2，3是1的子节点
深度有两种含义，上面的是定义1，按照层数划分
定义2，按照根节点到该点的最短路径的节点数为深度，如根节点深度为1.
{dotted startColor="#ff6c6c" endColor="#1989fa"/}
二叉树
分为：以下三种
1.空二叉树，2.左二叉树，3.右二叉树，4.完全二叉树
1. 0
------------
2. 0
/
1
------------
3. 0
\
1
------------
4. 0
/ \
1 2
完全二叉树可以用一个数组表述
由于完全二叉树，从上到下，从左到右增大/减小的性质
可以利用数组作为存储树的容器
其中每一个节点的父节点是 i/2 向下取整（i 是节点的总个数）
1
/ \
2 3
/ \ / \
4 5 6 7二叉树有最大二叉树，最小二叉树（主要根据根树的具体数据的排列来定义）
二叉树对于，增，删，改，查比较友好，尤其是查，每次只需查找一半，极大的提高了查询速度
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