【Lintcode】096.Partition List

题目：

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.

Example

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

题解：

Solution 1 ()

class Solution {  
public:
    ListNode *partition(ListNode *head, int x) {
        ListNode* left = new ListNode(-1);
        ListNode* right = new ListNode(-1);
        ListNode* l = left;
        ListNode* r = right;
        while (head) {
            if (head->val < x) {
                l->next = head;
                l = l->next;
            } else {
                r->next = head;
                r = r->next;
            }
            head = head->next;
        }
        l->next = right->next;
        r->next = nullptr;
        
        return left->next;
    }
};