用c++写的B树算法。包括插入、删除、查找等，供参考。-Written in c++ B-tree algorithm. Including insert, delete, search for information.

B-Tree of order 4 Each node has at most 4 pointers and 3 keys, and at least 2 pointers and 1 key. Insert: 5, 3, 21, 9, 1, 13, 2, 7, 10, 12, 4, 8 Delete: 2, 21, 10, 3, 4