【LeetCode】Swap Nodes in Pairs

http://oj.leetcode.com/problems/swap-nodes-in-pairs/

 

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){
            ListNode cur = head;
            while(cur!=null&&cur.next!=null){
                int temp = cur.val;
                cur.val=cur.next.val;
                cur.next.val=temp;
                cur=cur.next.next;
            }
            return head;
        }
        return head;
        
    }
}