Skip lists are a data structure that can be used in place of balanced trees. Skip lists use probabilistic balancing rather than strictly enforced balancing and as a result the algorithms for insertion and deletion in skip lists are much simpler and significantly faster than equivalent algorithms for balanced trees.
跳表（skiplist）是一个非常优秀的数据结构，实现简单，插入、删除、查找的复杂度均为O(logN)。LevelDB的核心数据结构是用跳表实现的，redis的sorted set数据结构也是有跳表实现的。
其结构如下所示：
所有操作均从上向下逐层查找，越上层一次next操作跨度越大。其实现是典型的空间换时间。
具体的细节，可参考维基百科http://en.wikipedia.org/wiki/Skiplist
- SkipList is licensed under the terms of the Apache 2.0 License. The license can be found at http://www.apache.org/licenses/LICENSE-2.0
