Remove Duplicates from Sorted List ,除去链表中相邻的重复元素

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;
	}