86. 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 l1(0);
		ListNode l2(0);

		ListNode* p1 = &l1;
		ListNode* p2 = &l2;

		while (head){
			if (head->val < x){
				p1->next = head;
				p1 = p1->next;
			}
			else{
				p2->next = head;
				p2 = p2->next;
			}
			head = head->next;
		}

		p2->next = NULL;
		p1->next = l2.next;

		return l1.next;
	}
};