LeetCode--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.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution 
{
public:
    ListNode *deleteDuplicates(ListNode *head) 
    {
        if(head==NULL || head->next==NULL)
            return head;
        ListNode* save = head;
        int flag = head->next->val;
        ListNode* pre = head->next;
        ListNode* end = pre->next;
        while(end != NULL)
        {
            if(pre->val != end->val)
            {
                if(pre->next == end)
                {
                    save = pre;
                    pre = end;
                }
                else
                {
                    save->next = end;
                    pre = end;
                }
            }
            end = end->next;
        }
        if(pre->next != NULL)
            save->next = NULL;
        while(head!=NULL && head->next!=NULL)
        {
            if(head->val!=head->next->val)
                break;
            head = head->next;
        }
        if(head!=NULL && head->val == flag)
            head = head->next;
        return head;
    }
};

LeetCode--Remove Duplicates from Sorted List II

原文：http://blog.csdn.net/shaya118/article/details/42677161