LeetCode OJ：Remove Duplicates from Sorted List （排好序的链表去重）

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.

简单的链表去重而已啊，遍历一边就实现了：

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode * p = head;
        if(p == NULL || p->next == NULL)
            return p;
        ListNode * prev = p;
        p = p->next;
        while(p!=NULL){
            if(p->val == prev->val){
                prev->next = p->next;
            }else{
                prev = p;
            }
            p = p->next;
        }
        return head;
    }
};

下面这个实际上比上面那个要快一点，上面那个是遇到一个删掉一个，这个是遇到一连串相同的就一起删掉，java写的，runtime比上面又不小的提高，代码如下：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head == null) return null;
        ListNode helper = new ListNode(-1);
        helper.next = head;
        ListNode p = head;
        while(p.next!=null){
            if(p.val == p.next.val){
                ListNode tmp = p.next;
                while(tmp.next != null){
                    if(tmp.next.val == tmp.val){
                        tmp = tmp.next;
                    }else
                        break;//找到最后一个和前面相同的节点
                }
                p.next = tmp.next;
                tmp.next = null;
            }else{
                p = p.next;
            }
        }
        return helper.next;
    }
}