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.
1,
/**
* 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 temp=new ListNode(0);
temp.next=head;
head=temp;
while(temp.next!=null&&temp.next.next!=null){
ListNode sign=temp.next.next.next;
temp.next.next.next=temp.next;
temp.next=temp.next.next;
temp.next.next.next=sign;
temp=temp.next.next;
}
return head.next;
}
}
原文：http://www.cnblogs.com/lilyfindjobs/p/4096377.html