86.Partition List
解法与思路：
将小于某一值x的结点加到pless所指向的结点，将大于某一直x的结点加到pbigger所指向的结点。需要注意内存泄露与将pbigger最后一个结点next置为NULL。

/**
 * 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 node1(0),node2(0);
        ListNode *pless = &node1;
        ListNode *pbigger = &node2;
        
        while(head)
        {
            if(head->val < x)
            {
                pless->next = head;
                pless = pless->next;
            }
            else
            {
                pbigger->next = head;
                pbigger = pbigger->next;
            }
            
            head = head->next;
        }
        pbigger->next = NULL;
        pless->next = node2.next;
        
        return node1.next;
    }
        
};