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
分析，因为是sorted的list。所以，重复的数字，会是连续的。
83. Remove Duplicates from Sorted List
原文：https://www.cnblogs.com/chucklu/p/10500384.html