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.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* partition(ListNode* head, int x) {
        
        ListNode left_dummy(-1);
        ListNode right_dummy(-1);
        
        auto left_cur=&left_dummy;
        auto right_cur=&right_dummy;
        
        for(ListNode *cur=head;cur!=NULL;cur=cur->next)
        {
            if(cur->val<x)
            {
                left_cur->next=cur;
                left_cur=cur;
            }
            else
            {
                right_cur->next=cur;
                right_cur=cur;
            }
        }
        left_cur->next=right_dummy.next;
        right_cur->next=NULL;
        
        return left_dummy.next;   
    }
};