Partition List

public class Solution {
    public ListNode partition(ListNode head, int x) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        ListNode fakeLeftHead = new ListNode(0);
        ListNode fakeRightHead = new ListNode(0);
        ListNode leftRunner = fakeLeftHead;
        ListNode rightRunner = fakeRightHead;
        
        ListNode runner = head;
        while(head != null){
            ListNode next = head.next;
            if(head.val < x){
                leftRunner.next = head;
                leftRunner = leftRunner.next;
                head.next = null;
            }
            else{
                rightRunner.next = head;
                rightRunner = rightRunner.next;
                head.next = null;
            }
            head = next;
        }
        leftRunner.next = fakeRightHead.next;
        return fakeLeftHead.next;
    }
}