标签：des style blog color io strong for div sp
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.
思路：添加一个空的头指针，每两个结点一组，先链接后一个结点，再链接前一个结点（注意链接完后将该结点的next指针置为空）。
1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * ListNode *next; 6 * ListNode(int x) : val(x), next(NULL) {} 7 * }; 8 */ 9 class Solution { 10 public: 11 ListNode *swapPairs(ListNode *head) { 12 if(head==NULL||head->next==NULL) 13 return head; 14 ListNode *p=head,*q=p->next,*r; 15 r->next=NULL; 16 head=r; 17 while(p!=NULL) 18 { 19 if(q!=NULL) 20 { 21 head->next=q; 22 q=q->next; 23 head=head->next; 24 } 25 head->next=p; 26 head=head->next; 27 head->next=NULL; 28 p=q; 29 if(p!=NULL&&p->next!=NULL) 30 q=p->next; 31 } 32 return r->next; 33 } 34 };
标签：des style blog color io strong for div sp
原文地址：http://www.cnblogs.com/levicode/p/3974626.html
