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; }
* }
*/
这题本来很简单，头一回不小心写错了，记录下来。常规写法多记录一个head。
递归：
public class Solution {
public ListNode swapPairs(ListNode head) {
if(head==null || head.next==null) return head;
ListNode temp = head.next;
head.next = swapPairs(head.next.next);
temp.next = head;
return temp;
}
}
近期评论