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：倒转链表中相邻的两个值
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* struct ListNode *next;
* };
*/
struct ListNode* swapPairs(struct ListNode* head) {
int flag=,tmp=;
struct ListNode* p=head;
while(p!=NULL){
if(==flag&&p->next!=NULL){
tmp=p->val;
p->val=p->next->val;
flag=;
}
else if(==flag){
p->val=tmp;
flag=;
}
p=p->next;
}
return head;
}