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* leftHead = new ListNode(-1);
        ListNode* rightHead = new ListNode(-1);

        ListNode* p1 = leftHead;
        ListNode* p2 = rightHead;
        ListNode* p = head;

        while(p){
            if(p->val<x){
                p1->next = p;
                p1 = p;
                p = p->next;
            }else{
                p2->next = p;
                p2 = p;
                p = p->next;
            }
        }
        p1->next = rightHead->next;
        p2->next = nullptr;
        return leftHead->next;
    }
};