Given a linked list, swap every two adjacent nodes and return its head.
For example,
Given 1->2->3->4
, you should return the list as 2->1->4->3
.
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ public class Solution { public ListNode swapPairs(ListNode head) { if(head==null||head.next==null) return head; ListNode faked=new ListNode(0); faked.next=head; ListNode pre=faked; ListNode cur=head; while(cur!=null&&cur.next!=null){ pre.next=cur.next; cur.next=pre.next.next; pre.next.next=cur; pre=cur; cur=pre.next; } return faked.next; } }
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时间: 2024-10-18 03:07:12