BPS使用 twist 指针实现 B 树

BPS 使用 twist 指针实现了B树，基于哈希表的集合，性能非常高，while using several times less memory and still maintaining order. The set introduces a new B-tree variety with superior search and edit qualities. Compared with the GCC distributed tr1::unordered_set, the new set is only 30% slower while using 3 times less memory. Compared with the ordered std::set, it is almost 4 times faster while using 5 times less memory.