Given a sorted linked list, delete all duplicates such that each element appear only once.
Example 1:
Input: 1->1->2 Output: 1->2
Example 2:
Input: 1->1->2->3->3 Output: 1->2->3
如果效仿 80. Remove Duplicates from Sorted Array II 要求每个元素保留不得两个，又该怎么做呢？
Given a sorted linked list, delete all duplicates such that each element appear only once.
Example 1:
Input: 1->1->2 Output: 1->2
Example 2:
Input: 1->1->2->3->3 Output: 1->2->3
link:{sourcedir}/_0083_RemoveDuplicatesFromSortedList.java[role=include]