LeetCode:Remove Duplicates from Sorted List II

Remove Duplicates from Sorted List II
Total Accepted: 70223 
Total Submissions: 262095 
Difficulty: Medium
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 .
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考え方:頭部に重複ノードがある場合を処理するために、「偽」のヘッドノードを追加し、
これも多くのチェーンテーブルの問題で使われているテクニックです.
code:

/**
 * 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) return NULL;
        
        //        “ ”   ，             
        ListNode dummy(0);
        dummy.next = head;
        ListNode *pre = &dummy;
        ListNode *cur = head;
        
        while(cur){
            
            while(cur->next && cur->val == cur->next->val) cur=cur->next;
            
            if(pre->next == cur) pre = pre->next; //      
            else pre->next = cur->next; //      
            
            cur = cur->next;
        }
        return dummy.next;
    }
};