leetcode:Partition List

/**
 * 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) {
        if(head==NULL)
		return NULL;
	ListNode *low = new ListNode(-1), *low_tail = low;
	ListNode *high = new ListNode(-1), *high_tail = high;
	ListNode *cur = head;
	while(cur)
	{
	    if(cur->val<x)
	    {
	        low_tail->next = cur;
	        cur = cur->next;
	        low_tail = low_tail->next;
	        low_tail->next = NULL;
	    }
	    else
	    {
	        high_tail->next = cur;
	        cur = cur->next;
	        high_tail = high_tail->next;
	        high_tail->next = NULL;
	    }
	}
    low_tail->next = high->next;
    return low->next;
    }
};