跳跃表(SkipList)是1987年才搞出来的新型高效数据结构，它的牛逼之处在于跳出来了树模型的思维，用多层链表的模式构造了Log(N)的时间复杂度，层的高度增加与否，采用随机数的模式。

	
	// ZSET use a specialized version of Skiplists
	// 以下是redis源码中跳表的定义
	typedef struct zskiplistNode {
    	robj *obj;
    	double score;
    	struct zskiplistNode *backward;
    	struct zskiplistLevel {
    		struct zskiplistNode *forward;
			unsigned int span;
    	}level[];
	} zskiplistNode;

	typedef struct zskiplist {
    	struct zskiplistNode *header, *tail;
    	unsigned long length;
    	int level;
	} zskiplist;