First, the definition of tree:
A set of hierarchical relationship consists of nodes; so long as the tree is called a tree;
Tree line and Artifact: https://www.cs.usfca.edu/~galles/visualization/
Second, the binary tree:
Characteristics: 1) values of all the nodes left subtree are less than the value of the root node;
2) the right subtree are greater than values of all the nodes of the root node and its value;
Example: the formation of a good chain structure;
Third, the balanced binary tree (AVL):
Characteristics: 1) on the basis of the binary tree, requires a high degree of difference between two subtrees shall not exceed 1;
1) each deletions will be by one or more rotations balanced binary tree;
Example: reinsert 123456 node;
Fourth, the red-black tree:
Characteristics: 1) node either black or red;
2) a timing black root;
3) All leaf nodes are null, and black;
Two child nodes 4) Red nodes are black, no two consecutive red;
5) Black any nodes on the path, the time constant equal;
ps: The Java terrMap and treeSet red-black tree is achieved;
五、B Trees/B+ Trees：
1) Each node has a plurality of values, two binary bits, three of the trigeminal, exceeding this value requires molecular node;
2) Balance nodes allow reading the depth decreases the number of IO path be reduced;
3) the balance data into the memory node is determined, it is faster;
六、B+ Trees：
mysql index is B + Trees achieved;
Features: 1) there is no non-cotyledonary node data, only the index;
2) so that regardless of check data, should be obtained from the leaf node, the number of times each query are the same;
3) reads the value of the index mysql, hash calculation only once, so the speed is faster than the B Tree;
