Remove Duplicates from Sorted List ：
Given a sorted linked list, delete all duplicates such that each element appear only once.
For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.
public ListNode deleteDuplicates(ListNode head) {
if (head == null || head.next == null) {
return head;
}
ListNode temp = head;
while (temp.next != null) {
if (temp.next.val == temp.val) {
temp.next = temp.next.next;
}
else
{
temp = temp.next;
}
}
return head;
}
Remove Duplicates from Sorted List II：
Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.
算法分析：区别问题1，这个是把所有重复元素都删掉，一个不留，所有要用两重while去重，上面一题去重时只需要一重循环。
public ListNode deleteDuplicates2(ListNode head)
{
if(head == null || head.next == null)
{
return head;
}
ListNode pre = new ListNode(0);//记录头结点，因为开头如果有重复元素，head将改变
pre.next = head;
ListNode temp = pre;
while (temp.next != null && temp.next.next != null) {
if(temp.next.val == temp.next.next.val)
{
int dup = temp.next.val;
while(temp.next != null && temp.next.val == dup)//去掉所有重复元素
{
temp.next = temp.next.next;
}
}
else
{
temp = temp.next;
}
}
return pre.next;
}
Remove Duplicates from Sorted List ,除去链表中相邻的重复元素
原文：http://www.cnblogs.com/masterlibin/p/5796979.html