一:经常会用到:Dummy Node,返回值是 dummy.next
2. Merge Two Sorted Lists
3. Partition List
Scenario: When the head is not determinated, 即head node 操作以后有可能发生变化
常见题目:
1. Remove Duplicates from Sorted List I, II2. Merge Two Sorted Lists
3. Partition List
4. Reverse Linked List II (Leetcode 上只有ii,没i)
5 Order list (merge的时候需要用到dummy node)