list对任意位置的元素进行插入，删除，查找都是极快速的，list的每个节点都有三个域：前驱元素指针域，数据域，后驱元素指针域-List any position of the elements to insert, and delete, find it is extremely fast, the list each node has three domain: precursor element pointer domain, data fields, the rear element p