不要求，讲数据结构时，参考一下。
In computer science, a linked list is a linear collection of data elements, in which linear order is not given by their physical placement in memory. Instead, each element points to the next. It is a data structure consisting of a group of nodes which together represent a sequence.
Linked list operations
The following code inserts a node after an existing node in a singly linked list. The diagram shows how it works. Inserting a node before an existing one cannot be done directly; instead, one must keep track of the previous node and insert a node after it.
function insertAfter(Node node, Node newNode) // insert newNode after node
newNode.next := node.next
node.next := newNode
Inserting at the beginning of the list requires a separate function. This requires updating firstNode.
function insertBeginning(List list, Node newNode) // insert node before current first node
newNode.next := list.firstNode
list.firstNode := newNode
Similarly, we have functions for removing the node after a given node, and for removing a node from the beginning of the list. The diagram demonstrates the former. To find and remove a particular node, one must again keep track of the previous element.
function removeAfter(Node node) // remove node past this one
obsoleteNode := node.next
node.next := node.next.next
destroy obsoleteNode
function removeBeginning(List list) // remove first node
obsoleteNode := list.firstNode
list.firstNode := list.firstNode.next // point past deleted node
destroy obsoleteNode 