LeetCode:Partition List

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

For example,
Given 1->4->3->2->5->2 and x = 3,
return 1->2->2->4->3->5.

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode* partition(ListNode* head, int x) {
12         
13         ListNode left_dummy(-1);
14         ListNode right_dummy(-1);
15         
16         auto left_cur=&left_dummy;
17         auto right_cur=&right_dummy;
18         
19         for(ListNode *cur=head;cur!=NULL;cur=cur->next)
20         {
21             if(cur->val<x)
22             {
23                 left_cur->next=cur;
24                 left_cur=cur;
25             }
26             else
27             {
28                 right_cur->next=cur;
29                 right_cur=cur;
30             }
31         }
32         left_cur->next=right_dummy.next;
33         right_cur->next=NULL;
34         
35         return left_dummy.next;   
36     }
37 };