leetcode——24—— 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.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* swapPairs(ListNode* head) {
            ListNode *dummy=new ListNode(0);	 
            dummy->next=head;	  
            ListNode *prev=dummy,*cur=head;	 
            while(cur&&cur->next)	   
            {   	       
                prev->next=cur->next;		
                cur->next=cur->next->next; //      		
                prev->next->next=cur;		   		 
                prev=cur;		
                cur=cur->next;	   	   
                
            }      	   
            return dummy->next; 
    }
};