[leetcode]86. Partition List划分链表

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.

Input: head = 1->4->3->2->5->2, x = 3
Output: 1->2->2->4->3->5

题意：

给定一个链表和一个值，把小于等于和大于该值的部分分别放到链表的一前一后去。

思路：

先分为两个链表

然后合并

代码：

 class Solution {
     public ListNode partition(ListNode head, int x) {
         ListNode leftDummy = new ListNode(-1);
         ListNode rightDummy = new ListNode (-1);
         ListNode left_cur = leftDummy;
         ListNode right_cur = rightDummy;
         ListNode cur = head;

         while( cur != null){
             if(cur.val < x){
                 left_cur.next = cur;
                 left_cur = cur;
             }else{
                 right_cur.next = cur;
                 right_cur = cur;
             }
             cur = cur.next;
         }
        left_cur.next = rightDummy.next;
        right_cur.next = null;
        return leftDummy.next;
     }