明日深圳行，心情紧张，写博文压压惊 囧
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原题地址：
https://oj.leetcode.com/problems/remove-duplicates-from-sorted-list-ii/
题目内容：
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.
方法：
递归做非常直观。
判断当前节点的值是否等于下一个节点的值，若不等，直接递归调用下一个节点；
若相等，则找到下一个不和当前节点相等的节点，并将其更新为当前节点，同时递归调用该节点。
全部代码：
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public ListNode deleteDuplicates(ListNode head) {
if (head == null)
return null;
if (head.next == null)
return head;
if (head.next.val == head.val)
{
while (head.next != null && head.next.val == head.val)
{
head = head.next;
}
head = deleteDuplicates(head.next);
}
else
{
head.next = deleteDuplicates(head.next);
}
return head;
}
}