索引链表实现细节，既有list的特点，又有map的特点。内部有两种迭代器实现。 list迭代iterator map迭代器kiterator 两种迭代器*，->操作都指向list节点。-Dictionary list(dictlist) realize detail, two kinds of iterator inside. one for list,the other for map. Both iterator point to the list node.