[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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        ListNode* pLess = NULL;
        ListNode** ppLess = &pLess;
        
        ListNode* pGreater = NULL;
        ListNode** ppGreater = &pGreater;
        
        ListNode* cur = head;
        
        while (cur)
        {
            if (cur->val < x)
            {
                *ppLess = cur;
                ppLess = &(cur->next);                
            }
            else
            {
                *ppGreater = cur;
                ppGreater = &(cur->next);
            }
            cur = cur->next;
        }
        
        *ppLess = NULL;
        *ppGreater = NULL;
        
        if (pLess)
        {
            *ppLess = pGreater;
            return pLess;
        }
        else
            return pGreater;
        return pLess;
    }
};