[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;       
    }