【LeetCode】Partition List

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) {
*         val = x;
*         next = null;
*     }
* }
*/
public class Solution {
public ListNode partition(ListNode head, int x) {
if(head == null || head.next == null) return head;
ListNode h1 = new ListNode(-1);
h1.next = null;
ListNode dummy1 = h1;
ListNode h2 = new ListNode(-1);
h2.next = null;
ListNode dummy2 = h2;
ListNode pre = null;
while(head != null){
pre = head;
if(head.val < x){
h1.next = head;
h1 = h1.next;
}
else{
h2.next = head;
h2 = h2.next;
}
head = head.next;
pre.next = null;

}
h1.next = dummy2.next;
return dummy1.next;
}
}