Given a linked list, swap every two adjacent nodes and return its head.
樣例
Given 1->2->3->4
, you should return the list as 2->1->4->3
.
挑戰
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; }
* }
*/
public class Solution {
/**
* @param head a ListNode
* @return a ListNode
*/
public ListNode swapPairs(ListNode head) {
// Write your code here
ListNode tempN=head;
int temp=0;
while(head!=null && head.next!=null)
{
temp=head.next.val;
head.next.val=head.val;
head.val=temp;
if(head.next.next!=null)
{
head=head.next.next;
}
else
{
return tempN;
}
}
return tempN;
}
}