[leetcode] 【链表】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.

题意

链表中每两个节点中，前后两个节点位置交换。比如1->2->3->4变成 

2->1->4->3

题解

略··看代码吧

/**
* 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) {
if(head==NULL||head->next==NULL) return head;
ListNode newhead(-1);
newhead.next=head;
ListNode *prev=&newhead,*cur=head,*next=head->next;
while(cur&&next)
{
cur->next=next->next;
next->next=cur;
prev->next=next;
prev=cur;
cur=cur->next;
if(cur==NULL)
break;
next=cur->next;
}
return newhead.next;
}
};