Given a linked list, swap every two adjacent nodes and return its head.
You may not modify the values in the list's nodes, only nodes itself may be changed.
Example:
Given 1->2->3->4, you should return the list as 2->1->4->3.
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode swapPairs(ListNode head) {
if(head==null || head.next==null) return head;
ListNode temp=new ListNode(0);
temp.next=head;
ListNode curr=temp;
while(curr.next!=null && curr.next.next!=null){
ListNode first=curr.next;
ListNode second=curr.next.next;
first.next=second.next;
curr.next=second;
curr.next.next=first;
curr=curr.next.next;
}
return temp.next;
}
}